Dwolla is an extremely innovative Payment API and the site allows you to transfer money with one of the least payment charges. We have covered Dwolla before here. Here is an interview with Michael Schonfeld, Developer Evangelist of Dwolla API.
SafeCharge has launched a full payment platform specifically designed for online marketplaces. Marketplace Manager hopes to address specific hardships and compliance requirements faced by marketplaces. Marketplace users access the entire platform through a single API.