I spent a year at the U of M before I transferred here, and I almost rushed there, so I know a little about the Greek system. There are ten NPC sororities: Alpha Omicron Pi, Alpha Chi Omega, Alpha Phi, Kappa Kappa Gamma, Kappa Alpha Theta, Pi Beta Phi, Gamma Phi Beta, Alpha Gamma Delta, Delta Gamma, and Delta Delta Delta. There is formal recruitment, which is held usually the third week in September, I think. Most sororities are pretty strong, and I believe all but two or three make quota. There is also spring rush for those that don't, so almost all groups are at total after spring rush. Total is somewhere in between 50-60 and quota in the past few years has been 16-17. I would guess that recommendations aren't necessary, and most girls don't have them, although of course they never hurt. The whole Greek system strikes me as pretty laid back and lots of fun to hang out with -- a good place to go Greek. I knew girls who went DG, Theta and AGD while I was there.
The Minnesota Greek webpage is under heavy construction right now, but it will eventually be up at
http://www.begreek.org/
Individual webpages are:
Delta Gamma
http://www.tc.umn.edu/~deltagam/Home.htm
Alpha Gamma Delta
http://www.tc.umn.edu/~alphagam/
Delta Delta Delta
http://www.geocities.com/mntridelta/
Alpha Omicron Pi
http://jwebc.com/aoii/