I searched on Outie and no one posted this so I thought I'd share this...
There's a software called Gomez Peer Zone (http://www.gomezpeerzone.com/) that leverages your PC's idle resources (such as unused processing power, RAM, and bandwidth) to test the performance of many of the world’s most popular websites.
It's quite simple, just leave your computer on and use it like you normally would. You earn based on the minutes and the country you're in. You also can paid for referrals as well.
You can make an account here: http://www.gomezpeerzone.com/application-apply/
If you like to try this out, I'd appreciate it if you can put my username (AyPn) as a reference; however, it's up to you. I'd greatly appreciate for the nice gesture though!
Read the FAQs for more info, or Google around.
PS: I started today and so far my online time has been 375 minutes and I've earned about $0.03.