The offensive linemen and tight ends will be doing the speed/agility drills today, which isn't the most exciting thing ever, and the defensive linemen and linebackers will be getting measurements done (they're done, actually).
Walterfootball.com is doing a good job of keeping track of all the numbers so check out their NFL Combine 2012 coverage page.
Here's the schedule for today - talk about the results below.
Group 1 (P/K, ST, OL), Group 2 (OL), Group 3 (TE)
Workout (timing, stations, skill drills), departure from Indianapolis
Group 4 (QB, WR), Group 5 (QB, WR), Group 6 (RB)
NFLPA Meeting, psychological testing, interviews
Group 7 (DL), Group 8 (DL), Group 9 (LB)
Measurements, medical examinations, media, psychological testing, interviews
Group 10 (DB), Group 11 (DB)
Travel to Indianapolis, registration, hospital pre-exam and X-rays, orientation, interviews