I've done some spot cleaning with the shop vac (wet/dry) and a mild solution of dish soap and water. My brother in law owns a carpet cleaning place and the "professional" equipment they use is pretty much just a powerful wet/dry vac with a sprayer attached-- spray it on, suck it out. You could use the carpet cleaning soap that they sell when you rent a machine, which is designed to foam less than something like dish soap.
... or take it to a carpet place.