The idea is to write a 50,000 word novel in thirty days. Those who meet or exceed that word count win. There are plenty of winner goodies provided through nanowrimo.org and participants have a finished first draft manuscript, which is an awesome accomplishment of and by itself.
Camp Nanowrimo happens in April and July and is designed to allow greater freedom in projects. Word count is adjustable and writing a novel isn't required. Participants can write plays, poetry, edit a project... I think there are more options than that.
This coming Saturday is the beginning of this year's July Camp session. We're set with a project and looking for cabin mates for the first time. If you've always wanted to write something, check out campnanowrimo.org
Several of our published works were Nanowrimo or Camp winners, including Beneath the Waves, Kedri Dancer, Old Tales Retold, A Sprite and Her Dragon, Dragonsbane Kingsbane, and more.