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!