HD quality web video and audio is now available with the latest Flash Player update.
Adobe Flash Player 9 now includes support for H.264 standard video, the same standard deployed in Blu-Ray® and HD-DVD® high definition video players, and High Efficiency AAC (HE-AAC) audio capabilities.
H.264, also known as MPEG-4 Part 10, is an open industry standard used by many, e.g. BBC (DVB-S, UK), SVT (DVB-S, Sweden), Levira (DVB-T, Estonia) and Elion (IPTV, Estonia).
For Flash developers there's a splendid selection of HD videos available on iStockvideo. They make more sense now.