Rogue Amoeba has released Airfoil 3.1. Airfoil is a tool for sending any audio to the AirPort Express, allowing you to send any audio to your AirPort Express units as well as other Macs running the complimentary Airfoil Speakers application. Airfoil 3.1 now provides full support for sending any audio to Apple TV 2.0.
Airfoil is the first and only third-party application to send audio to the Apple TV. Using Airfoil, you can send anything to the Apple TV, not just iTunes. Send audio from media players like QuickTime Player or RealPlayer, or web-based sources like Pandora, Last.fm, XM and Sirius.
Airfoil for Mac 3.1 is a free update for all owners of Airfoil 3. New users can purchase Airfoil for Mac for US$25.
A free trial version of the software is available, so you can start streaming right now.
More info here.