XRPIt is a deflationary currency and infrastructure component of the Ripple system.
Ripple acts as a decentralized exchange and payment network. It supports cross-currency transaction.
Ripple users will be able to pay for any transaction with any currency they choose. A user only holding EUR, BTC, LTC, WDC, QRK, or even DOGE will be able to make purchases from a vendor accepting only USD. All necessary currency conversion will occur instantly, at the point of sale, at the best available rate. XRP does all of its work in the background, helping to make it all possible.
It is exactly what crypto currencies need, as well as fiat, and the opposite of the centralized payment and exchange systems that threaten the community.
Ability to make cash deposits to its decentralized exchange system has just recently been added:
https://ripple.com/blog/ripple-now-multi-lingual-supports-cash-deposits-and-more/Ripple/XRP is the most misunderstood thing out there in the crypto currency community, while possibly holding the greatest promise. I consider it the best long term investment.
Ripple for Bitcoiners:
https://ripple.com/wiki/Introduction_to_Ripple_for_Bitcoiners