Chitika and adbrite are also popular but not like Google adsense. they don't have too many ads like Google and also not too many publishers.
- Adbrite in my opinion anyway maybe you should visit this link. http://www.rosswalker.co.uk/adsense_top10/ hope it helps.
I should mention here that you please stay away from the sale of the network as a text link text link ads. I have seen search engines penalize sites that are very involved in buying and selling text links without nofollow tag is what these sites. Although you can make money at first, yes, but in the long run, Google and other search engines may penalize or even indexes your site from their search results.
adsense is the best thing since Led Zeppelin. it has some alternatives, but nothing is closed enough to its awesomeness.
The best? I think adsense stable on their position. But for alternatives, it depends on your site. If you want run PPC, so chitika, adbrite, bidvertisers, innity, buzzcity are good choices. But if you run with wallpaper/image content, Imagespacemedia is also good. For adult sites, eroadvertising is my first choice. The last is Infolinks. This is my routine earning beside adsense. Adsense is not the only one, but still the best ever.
I'm thinking Chitika is pretty good, if you have lots of US/UK/Canada search engine traffic. It is paying me an average of 10-20 cents per click, which isn't as good as AdSense but it can very quickly build up if you've got a good flow of organic traffic. It also pays by PayPal, which is much more convenient from my point of view as a lot of my business is done via PayPal.