Magic Carpet Cleaner
I got some Dyzolv Spot Cleaner when I purchased my Dyson vaccuum, and it is absolutely magic. Stains literally disappear before your very eyes. This works on set in stains as well as fresh. I had some cat urine stains from months ago, sprayed this stuff on, and watched the color change back to the original carpet color before my eyes! No, it's not organic and probably not good for the earth, but for your carpet, it's mahhhvelous! Available at many retailers, see website above for one.
The label states "environmentally friendly"