Both Hulu and HBO Go announced that they are working on apps for Chromecast. Just like Vimeo and Redbox Instant did already, now joined by VEVO, Blip and Devour. With the original sources Netflix, YouTube, and Google Play the support for Chromecast is getting traction.
Chromecast just launched a week ago and is the USB dongle variant of the Nexus Q TV-Box that for now is to co-exist with Google TV. The HDMI-dongle is available for just USD 35, although currently sold-out.