I have been using Mean Green to shampoo my carpets for years. I use about 1/2 cup per gallon of water and it doesn't clog up your pump like pine oil will.
Cleaning Carpet
Make Your Own Cleaning Products
Using Vinegar and Water in a Carpet Cleaner
Homemade Carpet Cleaner Recipes
Using A Steam Carpet Cleaner
Homemade Furniture Polish Recipes
Using Shampoo as a Carpet Stain Remover
Dry Carpet Cleaner Recipes