Melaleuca is probably one of the best known companies that use the product advocate method.  You must first be enrolled by one of their existing representatives.  Then, you simply buy environmentally-friendly products from their line instead of the products you would normally purchase at a local store, like shampoo, cosmetics, protein shakes and bars, and a host of other such products.  Once you enroll others in the program, you get a cut of their product purchases.  No direct selling, no home parties.