Hi Cahrles,
I've never been to any of these places, but they're all on my "Some day..." list:
On the East coast - Disney's resort on Vero Beach (I think its about a 2 hr. drive away) or Amelia Island off of Jacksonville (this will be a longer drive, but I saw a feature on the Ritz Carlton resort there on the Travel Channel and it looked really nice).
West coast - Sannibel or Captiva island. A yr or 2 ago there was a trip report here where some guy from the UK (sorry, forgot his name) wrote about a few days they spent on Captiva and it sounded great - very relaxing, beautiful beaches. They went bike riding, kayaking in the mangroves, out on a boat ride to watch the dolphins. It sounded really nice and maybe a 2 - 3 hr. drive from Orlando.
Good luck!
~Linda