I've participated in Steephill.tv's Grassy Knoll Project before and enjoyed the results. The goal is to grassroot's media effort to collect photos and videos from a particular cycling event. Last year saw 1,733 photos and videos with start-to-finish coverage. The only problem was that it was a pain in the butt to participate -- after spending hours processing photos and videos to post to Flickr/YouTube/Google Video, you then had to spend more time uploading media one-by-one for the Grassy Knoll Project. As a result, I only sent a select number of images over the fence.
This time around things are integrated with Flickr (YouTube soon) so that all you have to do is tag your image and tell the Grassy Knoll Project to bring in your photos. One step contribution is a wonderful improvement.