First of all, you have to be very careful because being or paying a "professional" sex provider is illigal and could result in embarassment, fines and jail time. With that being said, many local papers will list "escorts" in their classified section, you may have to get the small entertainment papers that some cities have. You could also peruse www.craigslist.com and be sure to click on your city or the closest city to you. There's a link under services called "erotic" which lists call girls in that area.
This site offers escorts in North America, but they don't have many and only one had a review. This site is boston, but if you scroll down a bit, you will see the other cities listed, each city offers multiple listings of escorts including pictures, pricing etc. This google directory has listings by state, and each page has listings to other directories, there are many of them.