A filly, Rachel Alexandra, is taking on the colts, including Kentucky Derby winner Mine That Bird. In Europe, Asia and Australis fillies running with colts is the norms, but for some reason it doesn't happen as often here, especially in a Triple Crown race.
For entries:
http://www.usatoday.com/sports/horses/triple/preakness/2009-05-14-handicapping_N.htm
For entries:
http://www.usatoday.com/sports/horses/triple/preakness/2009-05-14-handicapping_N.htm