A few.

by San Pedro , More than 100 feet from Bob Davies, Tuesday, March 24, 2009, 17:43 (6272 days ago) @ domer.mq
edited by San Pedro, Tuesday, March 24, 2009, 18:16

Clock Rules

Clock stops on a first down in college - does not stop in NFL.
No two minute warning in college.

Pass Interference.

15 yard penalty in college. Spot foul in NFL.

Halftime is much shorter in the NFL - I believe it's only 12 minutes.