Air Video, a fantastic app that can transcode and stream video content from your Windows PC or Mac straight to your iPhone, iPod touch, or iPad, has just been updated to include support for multitasking and Retina display.
Your Windows PC or Mac needs a small piece of software installed to communicate with your iPhone, iPod touch, or iPad but once setup you can stream native iOS video content (MP4 and M4V) instantly to your device (rather than having to sync it over first via iTunes). Air Video will convert non-supported video formats (AVI, MKV, etc) and either store them for later streaming or stream them on the fly so you can watch now rather than waiting for later.