Free way to donate to charity

Many people will know about this already but I thought it was worth mentioning again: there is a range of websites which ask people to click on them once a day in order to generate a donation to a particular cause. The donation is made possible by companies advertising on the site. They are:

www.thehungersite.com
www.thebreastcancersite.com
www.thechildhealthsite.com
www.theliteracysite.com/
www.therainforestsite.com/
www.theanimalrescuesite.com

I must admit, I've never looked at the shop, I just click and go! Must check it out.