I've done the April daily poem for five or six years, with a break one year, and rarely did it generate a useable poem, but boy did it stir up the creative juices. The fun of it is doing it in a group, seeing what others post (when they dare, if they dare) and sparking each other through sheer audacity of trying. For me the effect was post-NaPoWriMo, the poems I wrote after that terrific marathon of 30 daily poems in a row, some as slim as three lines, some more than a page. The machine was well oiled by then and running well, and some of the poems after were keepers.
Many websites are up and running to gather NaPo-ers. The fun is in the workshop effect: we are all in it together. Here are just a few sites. It's not too late to join!
Potpourri of NaPo Writers' Sites
What is NaPoWriMo? Short explanation here.
Finally, a little bloghop to a writer blog that interests me because her new novel has similar themes to mine.