There is a lot of alternatives that exist. Here is just a few. AdBrite Bidvertiser Chitika Infolinks Intellilinks Pocket Cents Kontera Clicksor Exit Junction Dynamic Oxygen
There is actually not alternative to Adsense. Because, Adsense ads are really clean and adsense pays you with high CPC which no other ad networks do or can do. Anyways, if there is no way you can make use of adsense, then you can try Chitika. I recommend you to use buysellads. Because buysellads can sell more ad units if you are not using adsense.