Ken Davidian, manager of the NASA Centennial Challenges program, of which the 2007 Regolith Excavation Challenge is a part, has posted a number of videos on the challenge event:
Uncovering the Lunar Regolith Sandbox
University of Missouri-Rolla Description
TechRanch Tornado - Back End
TechRanch Tornado - Front End
Mendenhall BFD Operations
Duplex Engineering Excavator
Saturday May 19 Update: In comments on an RLV News post on these videos, Ken says he may be able to post more videos like these later. (One imagines that he's a busy person). Also note that he may also post some videos from the recent Astronaut Glove Challenge. Talk about an efficient low overhead cost Centennial Challenges program - the manager of the program doing the videos of each Challenge!
Update on May 20: Here's another one: Lunar Miner at NASA 2007 Regolith Excavation Challenge
Check the "regolith challenge" link below for more on the Excavation Challenge.