We recently traveled to the greek islands and had a fantastic time. Our favorite island was Santorini. Once on the island you need to rent a car. DO NOT rely on buses because the are usually full and there is no guarantee that you will be able to get on the bus due to so many tourists. We rented a car from AUTO4YOUSANTORINI and it was well worth it.
We had stopped at 6 other dealers before being lucky enough to find Mr. George Papalexis. He was the most honest and friendly guy to deal with and the first who did not try to rip us off or steal from us. He gave us a map of all the must see and do's on the island and was even kind enough to send us to restaurants off the tourist track.
I highly recommend doing business with someone who is honest and can help with any issues or questions. Don't waste your time pricing out other places, just go to the best priced and nicest guy to deal with at AUTO4YOU. He is a local so he can even help with lodging if necessary. We stayed at Hotel Villa Mathios which was a piece of heaven and quiet.