Of course, this is my opinion.  Please debate thoroughly.  I am also relatively new to Maine and can take being put in my place.  Please comment with your favs!!
1. The closest trails where I can get the biggest elevation gain, brilliant views and constant challenge: Big and Little Chick Hills (big and little Peaked mountain in other guidebooks)  I routinely do a 2.5-3 mile loop that goes up little chick, then up the beautiful, exposed ridge of big chick, then down the access road to the parking lot. I'll usually do 1-3 laps here.  1 lap is approx 2.75 mi with 1200' elevation gain, lovely views and great practice on the powerhike uphill and steep, gradual 1+ mile downhill (picture: looking at big chick from little chick hill).
2.  Kinda far away, but world class: Acadia National Park.  Approx 45 mi down the road, there is some of the best trail running, hiking and climbing in the USof A. This is where I get the majority of my 'home' long trail running in.  I can easily do a 20+ loop with 5000+ elevation gain within 30 mins of home (45 mins of bangor area).  Most of the north-south trails are highly runnable, while the east-west trails have big elevation gains in short distances, due to the geology of the mountains here (picture: summit of champlain looking northeast) 

3. The crown jewel of Maine: Katahdin and Baxter State Park. Despite the strict regulations here, you can get some major 4 season action at BSP. With a huge prominence, the area surrounding Mother Mountain of Maine is relatively flat. Because of this, you can get significant elevation gain in a relatively short run.  The Abol Slide trail is the perfect slope for a Vertical Kilometer world race.  Above tablelands, the peaks of baxter, south, pamola and hamlin are all well above treeline with the most breathtaking views in the northeast.  Only the presidential range of the White mountains challenges. 

4. The after-work go-to.  This seems ho-hum, but the Kenduskeag path weaves along the mighty Kenduskeag stream an in the steep canyon it creates.  Thoreau himself spent much time in Maine, focusing on the north woods and Katahdin, but he lived with his family in Bangor and walked daily along the banks of the Kenduskeag, appreciating its beauty in a way that only he can.  John Muir espoused the Sierra Nevadas, Thoreau espoused Maine.  Take an after work run along the 1.5 mile kenduskeag path a few times.  (Disclaimer, there are loads of sketchy characters near downtown--not sure if Thoreau experienced this as well, hmmm--run with friends or in the daytime with pepper spray, or just give such crazy looks that those characters won't want to mess with you) 

This is tied with Bangor City Forest, which is also easily accessible.  There are plenty of trails in here.  While relatively, flat, it has its variety of mildly technical trails and flat gravel paths for the beginner.  Make sure you know your way around, because it is a maze, even though it is relatively small!
5.  Great Pond Mountain Wilderness.  A wonderful secluded section of land in Orland/Dedham.  There are several small mountains just under 1000' that you can summit, but the vast, vast majority of hikers/runners sticks to the valley path and small spurs that are doubletrack gravel.  You can easily do 20 miles here never covering the same ground twice.  I love this area, though I swear I did encounter a Mountain Lion on East hill.  I thought it was a bobcat, but my 35 lb, 2' tall border collie sniffed her out in the tall grass at the summit.  The creature stood up and darted back into the woods.  I only got a quick glimpse, but the animal was cat-like with short hair and sandy colored and at least 3x the size of my dog. I have no doubt it was a ML and have no doubt that I was probably the first human up there in 6 months. Believe what you want, but I'm pretty freaked out to go back up there alone.  Still, hahaha, this is a great place!

6. Bald Mountain, Dedham.  The site of an old Alpine ski mountain, bald mountain seems small and unassuming, but its prominence rises nearly 800' in less than 0.6 miles.  This is my area of steep hill repeats, typically on the 'road' to the summit, which is used by hikers and maintenance crews of the cell towers.  There are multiple other trails surrounding the mountain, and in the winter, it is a fantastic place for backcountry skiing. 

7.  Ellsworth City Forest.  I've never run on such newly made trails.  This is a wonderful, empty place.  There is not much mileage to be obtained here and many of the trails are constantly wet, but the inner trail that passes along Branch lake is beautiful.  You'd think you were the only person on earth.  Not a camp to be seen on the lake in this area and in the 50+ times I've run through here, I've yet to experience the shores of this lake with another person.  In all, there is approx 7-8 miles of singletrack and doubletrack trails, much of it wet and relatively flat, but beautiful and secluded.  Shhhhhh, don't tell anyone else.

Please respond with your own Bangor area trail gems!! I've only been here a short while, but I have a knack for finding out trails in remote and urban locations.  I will lead some laid-back trail runs in the near future in these locales through GrassRoots! but let us know of others that you would like to lead! 

An end of the season race. So tired. So so tired. I had planned on doing the "beast of the east" 14 mile race, but opted instead for the 5 mile "classic" race.  We had 4-5 hours of driving to get home after the race, which started at 10am, and the family sentiment was, the sooner we got home, the better.  I could've just run the 14 miler fast (haha), but I don't think that would've been any faster than 3 hours. I knew the 5 miler would've brought me to the finish line in 1 hour or so.  So that was the plan.

Quentin Tarantino it back to Friday night--we headed west toward our sacred White mountains around 830pm. My wife, 19-month old human baby and 13 month old border collie baby left under the shroud of night.  Our destination...the Farmington, ME Walmart.  "Just park by the Burger King!!" the manager exclaimed. "You can't park near the entrance!!!!" Little did she know, I love parking 1/4 mile away from the shopping centre.  "Oh, we, will," I assured, excitedly! 

We pulled in around 1030pm and after tag-teaming bathroom breaks in the Wal-Mart (because the camper is already winterized for the season), we settled in for our slumber, which was interruped every 45 mins by ford f-250s and chevy 1500s peeling into the parking lot for a late-night something-or-other.  We survived the night, and after an early-morning shopping spree of milk and more milk, we headed westward on the serpentine Route 2. 

By early AM, Denny was sick as shit of driving and even more upset that we had the cahones to cross into New Hampshire.  We decided to make a stop in Gorham, NH, certainly the most under-rated town in the state. We did some swings and some playground action, and chilled in the northern shadows of the Presidential range of the White Mountains.  We then headed south on 16 to one of the centers of white mountain activity, Pinkham Notch.  From here, we embarked on a half-day hike to Tukerman Gorge, the epicenter of northeast backcountry skiing. Lindsay fared well and we hiked the 6 miles up and back in a little under 4 hours.  We chilled for an hour or so at the hermit pond lodge with other hikers (primarily Quebecquois) on their way to and fro. Denny got to stretch his legs and run around, while we (me) spoke awkwardly in broken French to les Quebecqois, who didn't appreciate my slaughtering of their language, but sportingly took a family picture of us.

Anyways, we scooted back down and we headed down the valley to the premier restaurant of New England:  99 Restaurant in North Conway.  And since the Red Sox won the night before, kids eat free; so we ordered a meal for Denny that we could snack on, without regards to his nutritional needs. After munching on much-deserved meals from our 6 mile hike/fast, we then began our quest to find a parking spot for the night.  This would prove to be a much more challenging feat than the hike.  North Conway village is more attuned to preventing overnight parking than child kidnappings, so we were turned away at the 50 acre empty, desolate, remote parking lot at Cranmore mountain. My superhuman wife may have prevented several acts of public disservice here for free, but, yea, they scoffed at these American knackers and pointed us elsewhere.  

Thus we headed for the seclusion of the mountains, like moonshiners and rapists of yore. 12 miles up route 16 we parked in my "last resort" campground, plan #4, the overflow lot of Pinkham notch, where we had hiked just several hours before.  We parked at 630 pm and it was pitch black by 7pm and raining vigorously, so we had no choice but to sleep!  The natural cycle of day and night is a beautiful thing and we took great heed; sleeping by 8pm is what nature intends when the sun is set!  Aside from an unnamed baby waking 5-6x and significant rainfall and wind, we basically slept until 7am, when we set southward to Echo lake for the main event.
Not wanting to monopolize the entire day, I decided to drop from the 14 mile to the 5 mile trail race.  This was a good choice, as I later found out, because I could eat a burrito, win a few prizes, and head homeward in the time it would take me to get to mile 9 of the 14 miler. (why would I ever do a long race again!!)
The day was supposed to be terrible; the forecast was for more grizzly weather like we had endured in our camper, Explore, the night before, high on the mountain pass at Pinkham notch, but yea, this was not the case.  The clouds broke and Whitehorse and Cathedral ledge stoodfast in our presence with a breathtaking view.  Still, haste was the goal, and the 5 mile race I did.
The course was beautiful--even though I had hiked most of the running route over the years, running it was different, primarily because it was faster. Only science will tell why this was the case.
Anyway, I took off fast, 6-7 min miles towards Cathedral ledge, where the literal ledge forced me to powerhike. At times, like I am known to do, I literally climbed on all fours.  No one else I've ever known in a trail race has done this, but I assume, due to my large ears and upper limbs, my genes link me that much closer to our hominid cousins, the apes. 
As fast as my ape-like body could carry me, the first female caught me at mile 3.  And though my simian features carried me swiftly up the steep slopes of Whitehorse ledge and quickly down the red ridge trail, my bipedal gait was no match for Alison. (I know her name because I took the time to schmooze on the downhill. Strategy, folks, strategy.)  Unfortunately all that talking tired me out, so my strategy didn't work at all and she turned on the turbo as the trail flattened over the last 1.5 miles, leaving me to scurry in for 3rd place overall.  

The only reason I was 2nd male/3rd overall was because of the lack of participation in this wonderful trail race, which shouldn't be the case!!  The course is perfect--none other is as great in the northeast for a 5 and 14 mile course.  The prizes excellent, the race directing superb (Acidotic racing, always a winner!) and the charity brilliant (Kismet foundation http://www.kismetrockfoundation.org/) which introduces kids to the world of climbing and mountaineering, who would otherwise never have the chance.  It is near and dear to my heart since my father used to provide the same experience to kids in a coastal community on Long Island, NY by giving them the opportunity to sail on his own small boat. This may not have made them sailors, but certainly it opened their eyes to a world beyond the streets of their own small town.  
In all, it was a wonderful trip and race. I'd love to do the long course next year, and I'd highly recommend it to any runner!