If you can find them, there are these little displays full of Carbona Stain Devils. There's a different little bottle for different stains: Blood, rust, ink, etc. These things are pretty amazing. However, the little bottle runs out pretty quickly, so if you’ve done something like, I don’t know . . . used a Phillips head screwdriver to kill a middle aged hitchhiker wearing a cowboy hat who tried to put his hand a little too far up your leg after you picked him up outside of Tuscon . . . or something . . . and you have blood all over the back seat of your car, it’ll take many bottles to get the blood out. As far as I know, Carbona doesn't offer the product in bucket sizes.
I put down a new carpet recently and then had some water damage that caused some rust stains on the carpet. I couldn't get them out for anything, until I got the Carbona stuff. I just squirted it on the carpet and the rust disappeared. Miracle stuff. I found it at WalMart. (Thanks, Sam.)