Last May, Facebook , which has joined MySpace as one of the leading social networking sites on the Web, launched "Causes," an application that enables its users to raise money for -- well, for just about anything nonprofit. Since then, more than four million Facebook users have joined Causes, according to the Non-Pofit Tech Blog . Some of those users have created Cause pages and initiated great recruitment and fundraising efforts, and some have given simply donated through Causes pages. Read more...