The vast majority of it is coming from PPC affiliate marketing (not ringtone offers though). I've heard people say it's comparatively hard to do, but I've had success with it. I have a couple of arbitrage sites running, but I haven't had much luck with them. I think I know how to make 'em better, but I haven't had a chance yet. I've also got a niche site running that's never had a single hit... not really interested in doing SEO on it, though - too much effort compared to this other stuff.