My Yogurt Formula (adapted from Harold McGee's article)
heat 1 qt milk--> 180°-190°
cool --> 115°-120°
temper and add: 2 Tbsp starter*
warm + still --> 4 - 8 hrs
More yogurt articles and recipes...
This recipe from the NYT:backstory blog article is basically the same as McGee's. And here is the article from the New York Times Magazine that it references.
Alton Brown's yogurt recipe is not quite as simple yet has lots of positive feedback. I'll probably not make it, but only because I don't happen to have on hand all the things it calls for. He does have some yogurt-based recipes that sound good.
And speaking of what to do with all the fabulous bacteria you just grew... the New York Times lists a ton of recipes featuring yogurt; from dip to dressings, soup to sorbet.
*Yogurt starter is just plain yogurt from the store initially, then reserve 2 Tblsp of the homemade yogurt to use as starter for the next batch.