All,
I was on sourceforge.net, and surprisingly clicked on one of their adsense links, and got a really good deal. I occasionally look at the links on my own site, as some are quite useful, not to benefit from the 'pay per click' which I find absolutely appalling, anyway.
Some of the affiliate programs appear to perform better, if you get the right mix. Adsense does not work for me, although it certainly covers site costs. I also like the google local search engine, which is more a convenience tool, than a revenue earner. I also use Freefind as a local search facility, but find the google results generally better. Just as an aside.
Best
Kevan