I spent a few weeks in Croatia this past summer. Dubrovnik is nice for a couple of days. Walk around the walls early in the day before it gets too hot and be sure to visit the museum of war photographs. You can really cover the city in a day or two. The drive to Split and Trogir is also nice and takes you through a sliver of Bosnia. We stayed in Trogir, which I thought was a very quaint and lovely little town, and made a day trip to nearby Split. You probably don't want to go this far but Plitvice National Park is gorgeous. We did visit many of the islands as we chartered a sailboat for a while so were free to go where we wished. Our favorite island by a longshot was Hvar. We chartered out of Dubrovnik and found that most of the islands that far south were not nearly as interesting as the ones further north. Next time I would charter out of Trogir.

I did do a trip report. If you're interested in details you can look for that in the Trip Reports forum under my name, or if you have questions feel free to email me.