Airparrot
Best solution for streaming audio and video to your Apple TV from an Mac or Windows PC... without using iTunes... is Airparrot.
Download it and install. It shows up in your system tray. As long as you are on the same network as your Apple TV, just right click the Airparrot icon and select Apple TV as your Airplay device.
http://airparrot.com
Then hook up your wireless keyboard and mouse and plop on the couch for some supersized web browsing.
It's 20 minute sessions for the free version, $9.99 for full and can gift to someone for $4.99 if you buy for yourself.