I use a small carpet cleaner for my carpet and cloth seats. The one I've got is the Bissell Little Green. It cost me about $80 at Wal-Mart. It comes with cleaning solution that you mix with water and has an option for heated water.
http://www.bissell.com/Products/prod...URPOSE+CLEANER
(mine is the one on the far right with two attachments and a heater)
For really stubborn carpet stains, I like Blue Coral carpet cleaner. You can get it at most auto parts stores or large retailers. I wouldn't trust it on the seats though.