Boxee, an open source media center with a focus on UI and social networking is now available on Apple TV!
Boxee will play any non-DRM content, and let users share information with each other and their existing social networks about what they’re watching or listening to. It will also aggregate all your entertainment (video, music, images) into one place and add in any RSS/XML/MMS feed (with mainstream content from sites like Hulu & ABC coming soon).
You can read more about Boxee in this article, or watch the video below.
The installation is very simple, thanks to an installer which formats a USB drive and sets it up to do the installation for you once plugged into your Apple TV.