The Daughter and I just made a passable ricotta-style cheese from two litres of whole milk (forget the brand, has a gold top on it), 1/4 cup vinegar, and some salt and chives. You bring the milk to a boil, then stir the vinegar in, and take it off the heat immediately. It should separate into curds and whey almost instantaneously (if not, add a tiny bit more of vinegar). Pour it into a strainer lined with a dish towel (we couldn't find the cheesecloth) over a pot (to save the whey) and then cool it by running cold water over the curds in the strainer, then squeeze the liquid out. Break up any clumps, mix in chives and salt, wrap back up, squeeze as much whey out as you can, and hang it for an hour to let any remaining whey drip out.
It'll keep in the fridge for a week. It's a very light, mellow cheese that does not really melt. I intend to try it in ravioli, or possible in a veggie lasagna later this week. And sprinkled on salads. The whey can be used in baked goods in place of water, or to soak grains in, etc. I'm guessing the yield is about 1/2 litre cheese from the 2 litres of milk. (I won a prize in the County Fair a few years ago with this, except it was with garlic chives and chopped lemon balm. I would assume you could sub in any number of herbs to your taste.)
I think I've heard that if you use lemon juice instead you get a kind of Indian cheese.