Pretty much the most important scouting you can do before hand is look at pictures of other robots.
www.firstrobotics.net was mentioned earlier, and it is a GREAT source for info on robots.
Then you just got to go into Robot Showcast forum, and see if teams posted about their robot.
Look at pevious regional awards, and see if some of the winners are going to your regional...
Other than that, you really got to check out thursday's practice rounds, and go around to teams' pit area to check out their robot. That's the best way to see what a robot can do, and practice rounds will tell you whether a robot is working or not.
Mean while, pay attention to matches, so you have updated scouting data for teams you are playing up against/with.
Not too much prep you can do now... Just work hard at the competition.
Good luck!