We've tried a few different things at the college level. People will watch a press conference, provided it doesn't go too long. But if it's a stand-up or I'm on camera we try and keep it to 3-4 minutes. Nobody wants to see my ugly mug for much longer than that. We've had some pretty good success with these. I agree that brevity is key. Using photos or highlights really adds to the quality, too.
A few examples (and a shameless chance to drum up a few hits):
A 1-on-1 interview with a player mixed in with some highlights the school was able to provide us: http://www.huskiewire.com/multimedia/videos/?id=69
Our newest venture, Football 101 with a player: http://www.huskiewire.com/multimedia/videos/?id=80
A video diary from a bowl game: http://www.huskiewire.com/multimedia/videos/?id=57
High school, but two local kids agree to play for the local D-I football team: http://www.huskiewire.com/multimedia/videos/?id=70
Hope that helps.