AirPlay. It's not just for Apple products anymore. The video you see on the next page shows an XBMC install on a Ubuntu Linux box running an AirPlay client service. As with the AirPlayer solution I wrote for the Mac, the XBMC application advertises on Bonjour and can be played to directly from the built-in iOS video menus.
In addition, several people have contacted me to mention that they're working on Windows adaptations as well. The photo below is a preliminary peek at an in-progress project being built by @infectionfx.