Rock and Roll Hall of Fame in Cleveland, I have not been there yet, but I have been told you could spend two days there.
(IMHO)
The R&RHOF was an interesting visit. You can spend 3 hours or 3 days there. I believe the latest temporary exhibit is Women In Rock.
There was a nice Bruce Springsteen exhibit when we were there in 9-10.
However I'll add this - as nice as the place is there is little substance to most of the exhibits. I enjoyed the Seattle museum the Experience Music Project bankrolled by the "other" Microsoft honcho - Paul Allen- much more.
Dennis