Last two years I earned a lot with Google Adsense.

Is that only thing to earn money? No

There are lots of alternative PPC programs. But all of these programs, you need to have good  web traffic. But all webmasters are not getting huge traffic. So if you are a new webmaster or if your blog getting little traffic this is the stable review stream that you are looking for.

Also if you  are not a webmaster ,still you can earn money with out spending money. You just need to setup blog . That is Free and easy. I’ll explain that how to setup blog in the future.

ReviewMe   is the best way to earn money , if you can type reviews about product/services .ReviewMe  site pay minimum $5 for a review. you have to write at least 200 words.

I earn around  $ 100 last month . That is extra money . Since you write unique content , eventually your site gets lots of SEO traffic and you can put any other PPC programs such as Adsense /Adbrite etc.