For me, Affiliation Cash worked nicely when I was at uni and needed something that worked nice and easy. I had the advantage of a convergence of events that made it really profitable then, though.
It's good if you've got domains or blogs about various entertainment media (i.e. music, gaming, movies, etc).
Then again, I'm a little biased, I work there as an AM now
I still can't see how people trust Clickbooth... The crap that went down earlier this year has just tarnished them forever in my eyes.
Azoogle's good though.