Maine's three northern rivers are dam-controlled, so good rafting is available through the season. The Dead River has a limited release schedule -- open just a half-dozen times for rafting in early summer and fall -- smaller releases allow paddling in inflatable kayaks during the summer. The Kennebec River has monstrous waves just below the dam, then tapers off into a gentle afternoon paddle as you float out of a scenic gorge. The west branch of the Penobscot River has a challenging, technical section called the Cribworks at the outset, several serious drops and falls after that, and dramatic views of Mt. Katahdin along the route.
Raft Maine (tel. 800/723-8633 or 207/824-3694; www.raftmaine.com) is a trade association of white-water outfitters in Maine. Call their toll-free line, and they'll connect you to one of their member outfitters.