Seth Godin has come out with a new free e-book called Flipping the Funnel, with a version specifically for nonprofits. Here's how he describes the basic idea:

Marketing is a funnel. You put undifferentiated prospects into the top. Some of them hop out, unimpressed with what you have to offer. Others learn about you and your organization, hear from their peers, compare offerings, and eventually come out the bottom, as patrons, converts and supporters. If you’re like most marketers, you’ve been spending a lot of time trying to shovel more and more attention into the top of the funnel. After all, if you can expose your idea to enough people, you can afford to buy more attention, to run more ads, to put more people into the top. As we’ve seen, though, the amount of time and money you need to keep that funnel filled can explode your budget pretty quickly...

Here’s a different idea: What if we flip the funnel and turn it into a megaphone? What if you could figure out how to use the Internet to empower the people who like you, who respect you, who have a vested interest in your success? I call this group of people—your friends and prospects and customers who are willing to do this—your fan club. A new set of online tools makes this approach not just a possibility, but also an imperative for any organization hoping to grow. Give your fan club a megaphone and get out of the way.

Seth suggests getting your supporters involved in a way that promotes peer-to-peer communications using some of the Web 2.0 sites like del.icio.us, flickr and his own Squidoo.

I have also discovered a great software product, GetActive, that can facilitate this process for nonprofit membership organizations. In addition to its great advocacy tools, which I became familiar with as a member of the American Anti-Slavery Group, it offers a community module that allows your supporters to create their own webpages to reach out to their own social networks. A client of mine is going to be using this software for their outreach efforts, so we will see how well this module works in practice. The idea is right in line with what Seth is suggesting. The success of these approaches will depend upon how comfortable your supporters are with using online tools, and how easy you make it for them.