Guide to Buying Traffic
http://reencoded.com/2008/08/14/guide-to-buying-traffic/

Robbins, Kyle
ReEncoded
2008

Abstract:

While many niches depend on PPC search traffic, there’s a wide group of sites that benifit from bought traffic from individual sites. Often times you can get very high quality traffic that converts very well from niches that tend to deal in a more direct site to site type traffic deal, rather than 3rd party ad networks. This guide is mostly to be used when buying traffic from forums, from individual websites, and from “plug” type packages, yet there are many things that transfer over to more traditional PPC outlets.