After being banned from Google Adsense (I still don't know the reason why) I have used Adbrite as an alternative. It's no surprise they are shutting down. The ads they deliver are borderline suspicious and they don't make publishers any money at all. I have earned $0.07 with Adbrite whereas I could have earned $60 in the same time frame with Google Adsense.
Hopping on that "used Adbrite after getting banned from Adsense" wagon. I think I got banned because after some user requests, I packaged my JavaScript game that the Chrome Store was linking to as a .crx package and left in the ads (the .crx contents are exactly the same as the original website). I was on track to make $60/day with Adsense, ended up making about $50/month with Adbrite :\ Sucks that even that was apparently on the high end for that network.
I haven't been banned, but AdSense is incompatible with my preferred mobile framework (jQuery Mobile) without some ugly (and possibly TOS-violating) hacks. Other mobile frameworks are in the same boat.
I'd also be interested in alternatives (ideally, Google would fix the AdSense code so it works, but people have been asking for that for a while).
Having temporarily been denied Adsense earlier this year (subsequently reversed), about the only option I would recommend is well-targeted affiliate marketing. Clickbank (in my case) ended up making rather more money than equivalently-placed Adsense ads :)
Does anyone know good alternatives?