I've got one recipe, dunno your choice but I personally like it. Hope you'll like it too...
3 tomatillos, husked and quartered
1/2 bunch cilantro
2 pickled jalapeno peppers
1 (16 ounce) container fat-free sour cream
2 (1 ounce) packages ranch dressing mix
Place tomatillos, cilantro, and jalapenos in a food processor or blender. Blend until smooth and set aside.
Combine the sour cream and ranch dressing mix in a medium bowl. Whisk in about 3/4 of the green sauce; taste and adjust the heat level by adding more green sauce