Alex is off orienteering around Europe so I've been borrowing her Garmin 305 as part of my top-secret Otis mapping project. I've ridden at this place 5 times in my life now (3 in the last 2 weeks) and I'm still lost most of the time. It's easy to know what general area you're in but impossible to know exactly what trail you're on or how to get from point A to point B -- every trail winds around ridges and back on itself so much that covering 500 yards in a straight line can end up taking a mile of riding.
In other words, Otis freaking rocks, except when you're lost and the sun is going down. What you see above is about 4 hours of riding -- the blue line and the red line are from two different two hour rides Linnea and I did this week. The red line basically follows the perimeter, but everything inside it is an insane network of smooth singletrack.
If you're looking for a place to ride early-season, you can't beat Otis. It's down south so it almost never has snow, and the magical sandy soil is almost never wet. Even after a day of rain in Boston, there was nothing resembling mud to be found at Otis.
One of the tough things about Otis is finding information about it. It's one of those things where all the locals know everything but no one publishes anything useful online.
Otis Mountain Biking Resources:
Rage MTB info page
Any map you see of Otis should be taken with a grain of salt. There are so many trails in various degrees of use, it's impossible to identify and map them all. There are no signs anywhere at Otis, so once you lose track of where you are on a map (which will happen about 30 seconds in, when you hit four intersections that aren't on the map) you'll never find yourself again.
All you really need is a compass or a good sense of direction. There's lots of options and all the trails are great -- as long as you don't have tight time constraints it's more fun to just go explore than to try to figure out where you are all the time.
It's about a 75 mile drive from Boston, so it's just over an hour if you keep the pedal to the metal. If it's 42 and windy out and you're looking for an alternative to riding on the road (or in the basement), head down and check it out. It's smooth and twisty and super fun -- you don't need full suspension or lots of mtb experience -- so even you roadie types should try it.
I'm thinking about getting a Garmin myself after experiencing the joy of looking at routes in Google Earth -- so maybe someday I'll have a definitive Otis map to post here.