There was a suggestion I read for a campaign to raise funds for a venue that was going out of business. The idea was to take donations and also sell off some photographs they had.
This reminded me of the NPR fundraisers, where they are asking for donations but at different times and for different amounts you get certain gifts in return.

So, here is the idea: Someone starts a fundraiser for $10,000 and with it posts the 10 gifts they are giving away, and the ten highest donors get to pick (in order of most to least) which gift they want. This can become something like an auction, where you might keep going back and making your donation bigger if you’ve been outbid etc, and where the buy-it-now price is 51% of the tipping point.

Here the incentives to give are shifted, and a donor who really wants a particular gift might go on to evangelize for purely selfish reasons.