The Island of Mustique (Part Of St. Vincent and the Grenadines) is fantastic.
Very low key. Interesting people and guests on the island.
We went for a trip in the fall of 2006 and will return this spring and yearly thereafter.
Highly recommended, but getting there is a bit challenging as only prop planes can land on the "runway" (not much longer than many of your driveways ), but htey are easily chartered from Barbados, St. Lucia etc...
Brian

 

Went there last year and though it was nice, didn't think it was the end-all be-all of Caribbean islands. It was fun that golfcarts were the modes of transport, and the little town was so tiny it could barely be called that. We stayed in a villa, which was nice but pricey. Thought the snorkeling and swimming (too rocky near the shore) wasnt so good, too. Here are some pics from our trip though...

 

which villa did you use?
We stayed at Bali Hi the first time, but are considering Tortuga for the next trip.
We loved Cocktail hours at Firefly and hanging at the beach below Jolies Eaux (sp). I can't post any pics of me and the wifey (she was nearly naked the whole time)
B

 

My wife spent a lot of time on St Barts beaches topless, so I enjoyed it there. Mustique we were with my parents (and son) so not so many opportunities.

The first villa we stayed at was Blue Waters but we left after a day or two because the water completely stopped working. I don't remember the next villa's name but it was right next to Tommy Hilfigers huge estate there...

 

we intitially looked at blue waters, but chose bali hi for the "view" and privacy.
we met Lawrence Stroll (he's Tommy's business associate) while there. as well as Elle Mcpherson and Tony Blair.
really cool people.
B

 

I don't think we saw any celebs while we were there...

 

we walked of the puddle jumper plane and i was getting the "paperwork" done. My wife was sitting there next to the most gorgeous woman. they start talking casually. after the 10 minutes at 'customs' i walk over and my wife says "Hey brian, meet Elle".. i almost fell over. My internal dialogue was something like "( i used to have posters of you on my bedroom wall)"
instead i just muttered a sheepish hello and went on our way. We saw her and the kids several more times over the next 9 days.