The British Foreign Office provides up-to-date information for travelers to Turkey. They offer information and addresses of British Consular Services Abroad as well as practical tips and health information. They also offer a new service you can sign up for that sends you updates on any country you request!
The U.S. State Department has information on travel safety and precautions. If you plan to drive a car, they also have an excellent Driver Safety Briefing that includes translation of road signs.
Street Crime in Turkey is another important consideration. You can find information at the US Embassy’s Ankara website.
The U.S. State Department encourages its citizens visiting in Turkey to register either with the Embassy in Ankara or the consulates in Istanbul or Adana.