Top Nonprofits' list of the top nonprofit organizations tells a story of how different organizations marshal their services to make a global impact, whether it's a modest outfit with a few thousand members or a powerhouse with millions of participants. 

This snapshot pulls in a lot of the nonprofits you'd recognize, some you might have forgotten about, and a few that you never knew were nonprofits in the first place. The results are ordered against a few factors: its web rank (1/3 weight, from a number of sources that measure traffic, page rank from Google, and other inputs), its social media engagement (Facebook and Twitter only here, both contributing to 1/3 weight) and its Charity Navigator Rating (1/3 weight). You may quibble with the rankings, but one thing is clear: the cause is noble in each case.