As of March 2013 Ripple is a new decentralised currency much like Bitcoin.
Ripple is built on the coloured coin idea. All the coins are already minted, and you have to buy a coin at the rate they advise. You can then send the ripples to whomever you require and the reciever can then exchange them for regular currency at the other end.
Ripple basically acts as one large exchange, the exchange being integrated into the system. Ripple is brand new, and is still to prove its place in the online payment market.