Clearwater and St. Pete beach are fun, even just to go and hang out at. I'll occasionally do that.
If you don't mind driving to Tampa go to MOSI, it's awesome. Orlando Science Center as well. Grand Prix Go Carts out by Orange Blossom are really cool, not like the Go-Carts you see on I-Drive, they go about 60mph. For food I HAVE to recommend Junior Colombian Burger, and almost surprised it didn't show up sooner. If you haven't been to Ale House for drinks this is your trip to go.