I'll be forever grateful to my college roommate's friend, who showed me how to make this delicious tomatillo salsa. Tomatillos are green and come in a little paper husk- they look a lot like green tomatoes, and they make a fantastic salsa verde.
I highly recommend starting with part of one pepper, then gradually adding to the salsa until it's hot enough. Note that it does take a little while for the spice to fully set in, so unless you really like spicy food, err on the side of 'too mild'.
This recipe for Tomatillo pulled chicken sandwiches also looked delicious.