Turkish cuisine is one of the richest of the world. Fusion of various cultures is also reflected in the food of the country. You can taste an extreme range of dishes which are mostly meat based. There are also very delicious vegetable based dishes of Aegean and Mediterranean food cultures. You can easily come across unique dishes from every region and even every single city. If you are not a vegeterian, don't leave the country without at least tasting the following: sish kebap, manti (Turkish ravioli lets say), gozleme (Turkish crepe), iskender (doner kebap as you may already know), lentil soup, kuru fasulye+pilav (beans and rice cooked in special Turkish way of cooking), and many more...
Turkish deserts are worth tasting. However, be aware that they might be a little heavier than the tastes you are used to. So, don't eat too much but try baklava, kazandibi, and Turkish profiterol as for my advice.
For more information and pics; http://www.turkishembassy.org/artculture/cuisine.htm and
check http://www.about-turkey.com/cuisine/ are good sites to check.