Wikipedia is ranked the 6th most popular in the world (fifth most popular in the US), so it might come as a surprise that it has only a staff of 10, and the rest of it's enormous success is built on volunteers. Wikipedia is a non-profit. (Cash-strapped non-profits: think about that next time you're wondering how you'll get everything done on your current budget.)
If you have a second, check out Wikipedia, which is trying to earn $6m through donations. They're asking for it in the best way, which is to put a prominent request at the top of the page, remind people how useful Wikipedia is, and tell donors how much they count on their support. All in just a few words. A strategy any nonprofit can follow to raise funds.