Much has been made about Google's $35 Chromecast dongle, which lets users stream their desktops and video to large screen TVs, but there is now a similar application for the Raspberry Pi that offers some of the same functionality: PiCast. Its developer has an informational page up here, where he notes: "I thought what do I have that I could use w/HDMI [licensing] and wouldn't be terribly hard to do? My Arduino? Nope BUT my Raspberry Pi can do it all, literally and [at the] same price as the Chromecast."
You can watch PiCast in action here. Essentially, you install the required software on the Raspberry Pi, and then you can send video and other content found online through the Pi to a TV. The project is early in development, but there is a GitHub repository here.