2014 ---in progress, playlist will be increased as reveals become known
2012: (Reveals and several prototyping videos, too)
The playlists from the earlier years don't have many videos. Still, I think it is interesting to see how other teams solved the challenges in the games.
Here is a comprehensive playlist of video clips produced by various FIRST teams, highlighting teams and their 2013 robots. There are over 90 of them in the list.
The YouTube channel I've posted for Firebird videos.