Google's developer preview SDK for Google Cast -- the streaming technology that's powering the Chromecast hardware -- is up and running. It looks like adding Google Cast support will be ridiculously easy with little coding overhead for anyone who wants to jump on the bandwagon.
Although the Chromecast stick we ordered here at TUAW will take a couple of weeks (at least) to arrive, the iOS SDK is already live and an iOS-specific project can be found over at Github.
It consists of an app that more or less runs (you may want to comment out the bits about the playProgres