RTexasF mentioned my favorite carpet/fabric cleaner, although I mix 6 parts water to 1 part woolite. Tough enough to clean most grime, yet gentle enough to not cause damage or even need rinsed. For large areas, simply spray, scrub lightly with a soft scrub brush, and vacuum up with a steam cleaner or shop vac. Small areas can be done by spraying and blotting/light rubbing with a rag. Works extremely well on vinyl and leather, too.
For extremely tough spots, I use Tuff Stuff, followed by Woolite/Water.
Dave