I'll second (or third?) the recommendation for Hvar - I spent a few nights there this past summer and really enjoyed it. I also enjoyed Korcula, which was much quieter than Hvar and provided a great place to rent bicycles and explore.

Rather than renting a boat I ended up traveling exclusively by ferry. It was a little more limiting as we had to plan our stops by the ferry schedule, but it was a cheaper option than renting a boat, and we met loads of great people.