Due to the Ottoman Islamic laws banning alcohol (the word used in the religious texts was "sarap", which in Turkish specifically refers to wine, and hence beer and raki -- the anise liquor that kaysyrahsyrah mentions -- remained available), Turkey has been void of any wine making history since before the 1300s. Only after the revolution in 1923 has Turkey been able to access wine, and only in the past 10-20 years have any attempt at serious wine making been done in the country. Kavaklidere (Ankara) and Seneler (Kayseri) are two of the better producers of wine in the country, but still utterly forgettable in the broader wine world, but if you are truly curious and you really feel the need to try Turkish wine, those are the two producers I'd try to stick to.
In general, however, I would advise against consuming wines in Turkey at all, since the domestic stuff is bad and the imported stuff is very heavily taxed, plus you'll find that many restaurants don't really know how to store wines and will have very poorly chosen lists. Therefore, you're really better off taking KSS's advice and sticking to the domestic beverages like beer (Efes Pilsner is easy to drink) and raki (Efe, Yeni, and Tekirdag tend to be the better brands and Efe in particular, since it is the newest of the producers, seems to have the best production standards for consistency and for creating a formula that is relatively smooth and doesn't cause wicked hangovers for some of the more sensitive drinkers).
Pass. Pass. Pass.
Give them a shot, but don't expect a lot.
I was there 8 years ago and tried everything I could get my hands on, and it simply doesn't compare to a first-tier wine making country. A friend of mine was there last year and had nothing good to say.
Drink the beer, and if you're crazy, the anise liquors.