
Participants from the USA, Canada, Japan, China, European Union and former USSR countries can obtain a tourist visa to Turkey upon entry with a valid passport and a fee (i.e., 20 USD for US citizens).
Participants from other countries should check the rules for their own passports with Turkish Consulates in their countries.
For more information please take a look at the page http://www.mfa.gov.tr/default.en.mfa.