Google adsense is great to earn money but when you are first starting out it isn't always enough. A couple of other adsense sites that I have been using are WidgetBucks and Chitika.
WidgetBucks uses adsense widgets with pop-under ads. You earn more and you also earn 15% for twelve months per referral. If you are running more than one blog or website make sure that you add each of your sites to their list. Otherwise you will see only page impressions and no earnings. When setting up your ads also make sure you set up each ad for each site individually shortcuts can be damaging. Take it from somebody who learned the hard way.
Chitika is the other adsense that I use. They don't seem to really pay very good, but it does help your google adsense clickthrough rate. Chitika seems to make your google adsense clicks worth more. It also help you come up in the search engines. If somebody does a search for mortages for example, your blog will come up even if your blog has nothing to do with mortages. Chtika also counts your google adsense clicks towards your chitika. That means if you receive two google adsense clicks that is equal to two chitika clicks as well and you end up earning double. If somebody visits your blog directly they will not see the Chitika ad unless they recently did a google search for something that a chitika ad has.