Some of the boat trips are also worth going on. We did the 12 Islands and it's a full day with lunch, swimming and even a little ice cream man thrown in at some point! Cost about a tenner each I think.
We did the Dalyan delta along with the mud baths last year and that was also a fantastic day out.
One word of warning though - the organised trips will usually stop at a Carpet showroom or Diamond centre - take my advice and stay on the coach! Unless you like the hard sell.