I'm not sure about 4 year institutions, but most of the two year colleges offer free tuition for seniors. You still have to buy books and pay fees, etc... but the tuition is free. The catch is that if the class is full, your getting kicked out. It's only available to partially full classes, and I think you are limited to only so many hours per semester.

The closest college to me is the State campus in Centre, AL and this is what they say...

"This program allows students 60 years of age or older who have met admissions requirements to receive tuition waivers for college credit courses on a space-available basis only. Space-available basis requires registration during the late registration process. The scholarship will not apply to repeat classes, regardless of initial funding source. This scholarship can cover up to six hours per semester of in-state tuition only after all other forms of financial assistance have been exhausted."