If you're in the Raleigh area, do make it a point to visit the North Carolina Museum of Natural Sciences.  It was a pleasant surprise to find this great place, full of spectacular exhibits, interactive displays, and expansive, purposely designed spaces.  The museum has a little bit for everyone, and it's a hit with kids.  This wonderful experience, which can last between an hour and a day (or several days depending on how much detail you want to take in) is also completely free.  Check out their website frequently for special exhibits and events.