My favorite fixed-helmet-on-cam video is still this ski jump, but I think we should get a lot more like those because they are pretty cool. Here's a biker zooming through Whistler Mountain Bike Park, in Whistler, British Columbia.
You probably don't have the balls to go ski jumping. If you do, congratulations; I hope you're reading this in flight. For the rest of us, this video is a great (read: less scary) way to get just the smallest slice of that action. A piece you can safely chew and swallow.