YOGHURT!! Love it (my own version), the store bought......not as much. Too much stuff in it like sugar, thickeners and nasty fruit slimy stuff. And making your own is really cheap and easy. Just be careful that you don't get sucked into the old fermentation addiction. Before you know it you'll be making your own cheese, beer (beer, ohhhhhh) and the list goes on.
Here is how.
http://biology.clc.uc.edu/Fankhauser/Cheese/Cheese.html
TONS of info from someone who really knows what's up. My stuff is pretty much the same as shown in his yoghurt process. There are lots of other tutorials for yoghurt making out there and most are a lot better than this one. There are a few steps that other people skip, but i f you want a good and consistent outcome, this is where you learn.