Back in 2007, I took part in NaPoWriMo for the first, and so far, only time. Basically, you're challenged to write a poem a day throughout the month of April. I used my iPod to provide inspiration each day in the form of a random song, and quite a few of the poems I produced ended up published, albeit after some fairly lengthy tinkering later.
I'm still undecided about taking part this year. My excuse to avoid it is that April's going to be a really busy month (readings, hosting a readers' holiday at work, a friend's wedding, and more), but on the other hand much the same can be said of most months, so taking part would be a welcome dose of discipline in my writing life.
But whatever I decide (and I can feel myself edging towards taking part even as I write), there's now a new, simple to use website for all participants. Register on it if you want to be part of it, and enjoy a hectic, but potentially very rewarding, 30 days.