The Turkish Embassy, London
http://www.turkisheconomy.org.uk/index.html
The Turkish Consulate, London
http://www.turkishconsulate.org.uk/
The British Embassy in Turkey, Ankara
http://ukinturkey.fco.gov.uk/en/
Turkish British Chamber of Commerce and Industry
http://www.tbcci.org/
Ministry Of Culture and Tourism (in English) with virtual tours of many of Turkey's most famous tourism venues http://www.kultur.gov.tr/EN/ana-sayfa/2-0/20110702.html
Property related
The consumer guide - "How to Buy Overseas Property Safely"
http://www.aipp.org.uk/consumer/buying-guide-and-advice/
2010 Rental Income Tax Guidance for foreigners.
www.gib.gov.tr/fileadmin/beyannamerehberi/rental_income.pdf
Property Tax International. Experts in Tax issues in 15 different countries - including the UK, Turkey, Brazil, Spain and the USA. Comprehensive Tax information and advice for residents and non-residents. Tax returns, Capital Gains Tax, Inheritance Taxes.....take the headache out of your tax worries!
The Global Property Guide's Overview on Turkey (updated) http://www.globalpropertyguide.com/Europe/Turkey
Tourism
Didim Tourism Association http://www.didimturizmdernegi.org