buy bulk fan page invites. Run contests. Go to related forums and blogs and ask people to help the effort for free by "liking" the site or additionally help by sending $ with an optional photo. Use a donation button payment that can be optionally adjusted higher if people want to help more!. Post at milestones. "Keep spreading the word! We are getting closer to our donation goal!" etc... Ask fans to share the fan page url with any forums or mailing lists they follow where such announcements would be acceptable. buying invites is probably a good place to start.
Have done most of what you said.. I have even installed the ilike viral plugin www.bollocks-to-poverty.com I have no stuff to give away so can't run a competition.. thinking of creating a stop motion animation video though for youtube
Find a contest sponsor to pay for the prize like an ipod touch or something. And display the sponsor ad on the fan page. If the sponsor doesn't want to re-up then find new sponsors, but keep the contests going. Make liking the page part of the entry requirements to win. That's what sprout online is doing.
