Google’s terms and conditions have been very strict suchthat many web publishers are banned or disabled to use adsense adverts on their sites. Many are denied from joining the Google AdSense program, for some reason or other.
Generally most of the reasons are for generating invalid or fraudulent clicks.

Most appeals to Adsense Support were also turned down. So many publisers are looking for alternatives to Google’s Adsense.

The problem is that most of the alternatives to Google’s Adsense are not comparable or come close to what Google’sAdsense does.( A matter of facts ).

Adsense still rules in terms of Ad inventory etc, there are tons of other advertising programs that can you consider for your sites or blogs depending on your niches and demographics.

But again there are some pretty good ones.
You may want to research these first before joining:
www.publisher.yahoo.com
www.kontera.com
www.adbrite.com
www.chitika.com
www.chitika.com
www.etology.com
www.bidvertiser.com
www.clicksor.com
www.kanoodle.com
www.qads.qumana.com
www.quigo.com
www.bidclix.com
www.vibrantmedia.com
www.pheedo.com
www.turn.com
www.adversal.com
http://www.7search.com

There are many more available. Do a search and you will be gather more.