There are many sites through you can really earn on internet. Though it is not that easy to earn but still there are many sites available. Now, it depends on what way you want to earn on internet. Some sites like affiliate/referral sites gives you a chance of refer and earn commissions but for this kind of earning you need to promote you website, weblinks etc.
Other options are Online Data entry and one need to research a lot to find a genuine online data entry work. Although, online data entry can make good bucks.
One cool affiliate/referral site is co.cc where you need to refer people to grab a free domain on co.cc and you get few cents for every user referred who successfully completes grabbing a domain. Another site is Mechanical Turks which pays you as well for online work.
To know more similar cool ways, logon to http://earn.kunals.com/