Funny as Hell I had always heard of this movie from friends and read about it in an article about South Park. I think it's kind of funny that I found this in Borders on DVD, because this is definatly not something for that store.
Before South Park and That's My Bush, Trey Parker developed a movie based on a Colorado legend known as Alfred Packer, who apparently led a group of miners to find gold and eventually wound up starving and eating them all. So, it is technically based on a true story. All that being said, this is the funniest damn movie I've ever seen. Witty dialouge, odd humor, great musical numbers (any movie with a song called, "Hang the B****rd" must be gold), and, if you have the DVD, commentary that is funnier than the movie itself.
Don't know where you can find it besides the internet (you can try Borders, like I did), but whatever you do, buy this movie! I cannot stress that enough.