There are lots of different adventure races out there, from the more national events (Primal Quest) to the local coordinator that runs a small event. Anything from a sprint race to 12 hour/24 hour, multiday ones. The smaller events can be real fun in that there may be less teams, a more informal atmosphere, but the money/prizes, etc. are typically with the national events that get points that can qualify to the more prestigious ones.
There is a really nice free booklet that I get every now and then for the Mid-Atlantic region that lists everything from running 10ks, to cycling centuries, to bi/triathlons. They will also list Adventure races. The name though escapes me at the moment and that is for the mid-atlantic region but I'm sure they have a NE one. A typical outdoor's store, mountain bike store may have it on the counter. It's a great place to start to find events.
Good luck, and have fun. The races are a lot of fun but they are not cheap!
Jay