Cool new site of a friend of mine's
Yes, yes, it's a shameless plug, but www.veotag.com -- allows you to annotate videos online on the fly. Very very cool. It's a service run in part by my martial arts instructor Arkady Dudko. It's very cool; he's shown me some video clips of martial arts forms that he's taken and annotated (they're copyrighted, so I can't re-share them).
Browse through it at http://www.veotag.com/browse/.
I wish him and Scott Rhodes the best of luck with the service, it looks pretty cool.