Set Top Box. Plug it into my TV"s HDMI input, and watch video streamed from the LAN.
I'm hoping to be able to boot an internet OS like Joli OS 1.2 and run XBMC on top of it. I'm currently doing this using an old Dell Dimension 2400, (2.4ghz P4, 1.5 gbytes memory, Nvidia Geforce 8400 GS), and it works great except that like every other Linux distro I've tried on this hardware, video playback is choppy in the browser (hence one reason I like having XBMC installed--playback is silky smooth). rPi will hopefully eliminate this last remaining problem and I'll be able to drop using XBMC altogether... Like Chromium OS, Joli OS includes the Chrome browser by default which means not only do I have access to all of Joli OS's apps, but Chromium's as well. In addition, unlike Chromium OS, Joli OS allows you to easily access the local file system, access native (Linux) apps, access multiple workspaces, attach to network shares, etc. The reasons why I don't want to use XBMC alone include: navigation in XBMC is slow and awkward, you have to wait for plugins to be developed while the rest of the world accesses the same content directly in their browser and there’s no easy access to “local” apps. I understand that Joli OS 1.2 is built on Ubuntu 10.04 and that it may not support the ARM version used in the rPi, so that's the potential hurdle...