Have read up on these websites and they look totally legitimate, many positive reviews.
If you chooose to sign up (not necessary for click donations) there is apparently no risk of spamming, all genuine and trusted.
What a great cause, hard to believe just clicking, at no personal cost, will provide donations (Let's Click Away!) but that appears to be the case:
From Wikipedia, the free encyclopedia -
The Hunger Site is the original click-to-donate site created in 1999 that gets sponsorship from advertisers in return for delivering users who will see their advertisements. The Hunger site encourages visitors to click a button on the site, once per day, asserting that each unique click results in a donation "equivalent" to 1.1 cups of food. The Hunger Site is not a charity; it is a for-profit corporation which donates the revenue from its advertising banner to selected charities. Currently, these are Feeding America (formerly America's Second Harvest) and Mercy Corps.
Care2 is a social network website that was founded by Randy Paynter in 1998 to help connect activists from around the world. It has a membership of more than 17 million people. Care2's stated mission is to help people make the world a better place by connecting them with the individuals, organizations and responsible businesses making an impact.