I wondered the same thing about 3 years ago, where to buy decent traffic at a non-outrageous price? And more importantly, who would actually send the traffic rather than just abscond with my money? I began finding good sources of paid traffic, and put together a site to share those trusted sources with other webmasters.
By all means have a look and see if there is anything there that catches your eye....
Paid Traffic Source
Some of my sources have already been mentioned in this thread. Nice too see it.