I've been to these ones:
The Harry S. Truman Library in Independence, MO
The Richard M. Nixon Library in Yorba Linda, CA
I had planned to go to the Ronald Reagan one the day after the Nixon one because they're not far from one another. However, I was unable to because of car trouble.
I've also been to the Lyndon Johnson Library in Austin, TX, but I don't really remember it because I was a little kid.
I'd really like to go to the FDR one, the JFK one, and the Lincoln one.