**Important news flash: As of April 10th, 2014 you will not be able to purchase your visa upon arrival in Turkey.
So if you are planning a vacation in Turkey as a tourist or you have business, you can now go online and obtain an 'e-Visa' which is good for 90 days. "It's an easy 3 step process and saves hours of waiting in line", says Archaeologous. The e-Visa will then be returned to you via email usually within 72 hours or less. If you have plans for longer than 90 days such as work or study then please contact Travisa Passport and Visa Service.
This e-Visa is replacing the traditional visas that were always bought upon entering Turkey or stamped in your passport. So now, no more waiting in long lines at Turkish embassies or at the port/border crossings upon arriving in Turkey.
Go to this link for 3 easy steps and get your e-visa https://www.evisa.gov.tr/en/
Look what awaits you in Turkey: http://www.archaeologous.com/blog/50/video-istanbul-overview-offered-by-archaeologous/
For other helpful info go to: http://travel.state.gov/content/passports/english/passports/new.html