I've made a gallon of yogurt at a time using 4 1qt. containers, a cooler, and a heating pad. Prepare the yogurt as Knotted said (I heat the milk in the microwave, then add starter once it has cooled enough to not kill the cultures), then put the containers in a cooler with a heating pad on top set to low. Works like a charm. I only use about a TB of "starter" in each quart from a previous batch.

We usually drain each finished quart overnight with the paper towel and collander method. Man, I love that stuff!