There are some advertising sites, which will pay a few mBTC just for visiting the site.
My favorite one is coinad.com. Google knows many more .

Edit:/
Other cool offers are Earn Free Bitcoins & BitVisitor.
You have to visit websites for a few minutes (automatic after entering a captcha) and get paid for it...
Would be nice, if you use my ref-link: earnfreebitcoins.com?ref=15hruVg9qpmvby7vhmFQHWNEoQcSLJHzXt and www.bitvisitor.com/?ref=1BL2XkE9jKd5pmwTsUkd3v47usJWWxy5MK