It was already mentioned, but the Smith River Canoe race is a blast and one of the only (probably THE only, never heard of another one in 13 years) organized runs from Wentworth to Winnipesaukee.
See
www.lwa.org, the Lake Wentworth Association Web site. The race has many classes for canoes, kayaks, men, women, mixed, age, etc.... There is a dam at Crescent Lake that is lowered for the race and a short white water run up to a portage that lets you take your vessel to Back Bay (Winni..).
I've done it a few times, photographed friends doing it and had fun either way.