If you usually leave your computer on and cornected to the internet, or normally spend long time surfing then here are two links that you can earn money just by running these programes. They are perfectly safe as I have been running then for over a year now and have made some good spending cash.
The first is: Gomez Peer. Pays monthly directly into paypal account:
The other one is Green Horse ticket bar. Just click on image below:
I run both on my computer.
All the best