Let me know if you figure out a good solution for this. The only thing I could find to do this was PayPal. I've had lots of ideas for marketplace type of sites, but the stopper was figuring out a way to let sellers accept payment. Often individual sellers aren't making enough to cover the hassle/cost of getting merchant accounts set-up so going the IPSP route seems unviable.<p>Google Checkouts is also a possibility but lacks a strong api.