tom, you've probably already seen this:
http://www.flyer.co.uk/greece.php
...as posted by kyprianos Biris in 'VFR around europe' in this forum.
Not exactly what you're looking for but well worth the read. Includes details of trip to Skiathos amongst others.
For what it's worth, Skiathos is very near the top of my list of 'places I want to fly when I actually get a license'. Also, Samos (the approach to here on an A320 is 'interesting' - mountains on 2 sides and Turkish airspace on another - 90% turn to short final at about 300ft agl - want to try it myself) and some of the smaller islands that are normally served by Dornier 228's.
Good luck hiring an a/c and if you manage to fly out there, be sure to post a trip report!
PS Not sure if there's a club/rentals but there were several light singles on the apron at Rhodes when I was there a year ago. I've also heared of a flying club at Zakinthos which have a Pa28 but can't find the link any more.