Yahoo Publisher: First One, if you live in America, yahoo publisher network (YPN) is your best alternative to AdSense.
Chitika: This is one of the best ads network for anyone in the world but have some adequate your traffic to your blog.
Clicksor: It is also one of the best alternative to Ad-sense. Inline text banner ads on your website/blog.
Adbrite: This is fourth alternative (or 3rd, if you live outside USA). Please note, you may see very little earnings for first 20 days (or even a month) as they collect your website/blog statistics.
Bidvertiser: This option is advertising on your site/blog is a good situation.You can withdraw your earnings even $10 form it.