The Yahoo! Research Berkeley team built a handy hack demo viewer:
"You can see a list of all the hacks (including which hacks won the judges awards), you can launch URL demos for many of the hacks, and, best of all, you can jump to any hack instantly to watch it (no waiting for it to load or fast forwarding through the video to try and find things). We’ve also displayed the list of hacks directly on the video time line, which makes scanning around for hacks incredibly simple."
Check it out at: http://timetags.research.yahoo.com/hackdayuk