As of right now, I count 776 registered teams, distributed as follows:
I can do really neat analysis of things because I have The Blue Alliance database.
Code:
Teams Registered Event Name
38 BAE SYSTEMS Granite State Regional
34 Midwest Regional
20 New Jersey Regional
14 Oregon Regional
11 St. Louis Regional
23 Arizona Regional
18 Finger Lakes Regional
54 Greater Kansas City Regional
37 NASA / VCU Regional
16 San Diego Regional
22 Boilermaker Regional
13 Chesapeake Regional
17 Connecticut Regional
30 Detroit Regional
51 Florida Regional
23 Peachtree Regional
4 Pittsburgh Regional
26 Silicon Valley Regional
21 Wisconsin Regional
7 Buckeye Regional
10 Lone Star Regional
16 Los Angeles Regional
15 Microsoft Seattle Regional
32 Oklahoma City Regional
6 UC Davis Sacramento Regional
4 Waterloo Regional
19 West Michigan Regional
13 Bayou Regional
26 Boston Regional
12 Colorado Regional