You can make use of people-oriented social networking sites like fundable.com or chipin.com. These sites though low profile are ideal for contributing to charity or even funding for a common cause. In fact, any social networking site plays an influential factor in helping a lot of people contribute for a cause like Anti-Aids Campaign, Go Green movement, Save the Planet movement etc. Apart from social networking sites like Facebook and Stumbleupon, there are specialized sites like justcauseit.com and which are influential in raising awareness on social issues and collecting funds for improvement of the environment and other social causes.