Kaş is a super cool town with lots of great restaurants and bars and a nice selection of cheap pensions. Its a bit surprising since it doesn't have a real beach to speak of, but that may be why it is such a chill place - it definately attracts a hipper and more travel-savvy clientele than some of the other coastal towns.
From Kaş we went on a kayaking trip to Kekova and Kaleköy. Due to the land sinking (or earthquakes, depending on who you ask...), a lot of the ruins of nearby ancient Simena are underwater. It was a neat experience to paddle over them, although you can't see much more than some broken tiles and foundations, so it's not exactly the lost city of Atlantis we were imagining.
We spent the rest of our time in Kaş just wandering around the town, hanging in the square, checking out diving pictures from the area and eating dondarma (the thick and rich Turkish ice cream for which we have developed a serious addiction). We would definitely recommend Kaş as a great place to while away a few days if you are ever in the area.