1
Oklahoma has 7 Big 12 Championships
Nebraska won 29 Big 8 championships (24 outright and 5 as co-champion) and, prior to the 2010 championship game that Nebraska will play in, 2 Big 12 championships.
12
The Bulldogs have won two consensus NCAA Division 1-A college football National Championships and 12 Southeastern Conference championships.
12
One.
7
The Oklahoma Sooners have won eight Big 12 Conference championships, in 2000,2002,2004,2006,2007,2008,2010, and 2012 (with Kansas State.)
Alabama
Assuming you mean football..FSU has won/shared 12 ACC championships.
The Big XII has won 3 national championships.
Oklahoma has won 31 big 12 championships. I'm not sure of the breakdown by sport, however.