Craigslist.  It is a web site.  

I would proceed with caution when using CL.

Craigslist.org is a local sort of bulitin board and they have boards for every area of the country.  It is great if you want to find a used refrigirator or sell a car.  But the erotic services section (where you will find most of the escorts) is rampant with Rip offs, Upsell agency girls, and email phishing scams.  There are a few good ones on CL but it is really not worth the trouble sifting through all the muck when we have TER at our disposal.  

Best thing to do is if you find someone on CL and thay have a phone number copy it over to the search form on TER.  If it comes up with no results they are most like a rip off.  One out of 10 times you will actually come up with some results.  And these are usually not the "Best" TER has to offer, there adequate and not a rip off just not the cream of the crop.  This has been my experience anyway in the LA area.