This is an easy yummy way to use fresh tomatillos. We made this a lot last summer, and as we just got a batch of tomatillas from the farm (and the cilantro, garlic and chilis, too), we made some last night. It is from Rick Bayless', Mexican Everyday, which is a great book.
4 medium tomatillos, husked, rinsed, and quartered
1 large garlic clove
hot green chilis (he recommends 2 serrano or 1 jalepeno), stemmed and roughly chopped
1/2 - 1/3 cup loosely packed, roughly chopped cilantro
Put it all in a blender or processor with a little (1/4 cup) water and 1/2 tsp salt. Get it to the consistency you like (I like it sort of runny). When you put it in a bowl you can add extra water if it needs it. Season to taste. It's best eaten right away.
He includes lots of variations (add parsley, add lemon zest (we do that), try mint, etc...)
I chopped the chilis seeds, pith and all because we like it spicy, but adjust for yourself!