ExactSeek.com seems to be offering a pretty good deal on their sponsored ads. $12 for unlimited clicks for 3 month seems like a steal.
I tried it due to the prices. I closely tracked where the clicks came from and they weren't targeted at all so I never signed up for it again. I'd forget that one.
What's your website and which words did you purchase? I'm thinking about purchasing the keywords "wholesale" which is half gone.
Many of the good sites that your ads will show on is there's. Many of the other sites are ppc search enignes where some or most of them don't get much traffic. Just because your ad gets shown on a lot of sites don't mean much. I had them come to me asking if they could put their ads on my search engine when it use to be one, but then I changed it now to something else. I declined their offer at the time. I have used them for the keywords "games". I don't know how much traffic I got for that and they were still rather new with this program then I think, but I'm sure it was not over 10 uniques a day. I think it may have even been under 200 a month and the games keyword is a popular one.