HD-DVD and Blu-ray aren't the only HD disc formats out there; there's a handful of alternative formats (mostly based on red lasers) that have tried, or are still trying to get a space on that home entertainment shelf.
Forward Versatile Disc (FVD) This is a format created by Taiwan's Industrial Technology Research Institute and Taiwan Advanced Optical Storage Research Alliance. It uses a red laser, just like DVDs, but can hold up to 6GB on a single disc layer. It uses the Windows Media Video 9 and Windows Media Audio 9 Professional codecs, which allow up to 135min of HD video to be stored on each layer. You can get more information here.