Google now has an option where you can pick the sites that your ad goes on. Its a pretty good way to get a targeted audience
buying is links can have abad effects with your page ranks. you can use artricles marketing and submit to directory.
You can try 2space.net you can place free ads. I have paid more then 500.00 in ppc and only make 140.00. I don't know what I'm doing wrong.
Buying traffic is like buying leads, its a suckers game. Create your own leads is the ONLY way to go. Dont be afraid to do it , to make big money you have no other choice!
As far as 'buying' traffic is concerned, Google Adwords and Yahoo are the best - they work well and I get plenty of leads from them.