Three Useful Links for HTML Media in a Prim:

• Knowledge Base with Torley Tutorials
  
• HTML on Prim & build-in web browser in Second Life

The next is untested and this requires the old Release Candidate since the Second Life 1.22.11 (113941) Mar 6 2009 does not have a plugin folder. Beware this is therefore experimental, not on the SL Main branch now for some reason.

• How to: Get Flash Player to work in Second Life