wheel - 6:00 pm on Oct 5, 2011 (gmt 0)
Doesn't OpenX have an ad network?
I'm not up to speed on this end of the biz completely, but there are certainly some niche, non-general, and highly targetted ad networks available. I've mentioned previously that I run one in my niche, in my country. I've got pretty much all the high quality independent sites running my ads.
In my country I know there's at least one big one - sorry, I forget the name, but they went on about billions of impressions, all at very low cost. And I know there's at least two companies that do exactly what I do (in my niche) that only work in the US. There must be others in other countries as well.
In the end, if you're not a generalist, try looking for niche ad networks. There must be stuff in niches like technology and other competitive niches.