Non-profits and charitable organizations have so much to gain from using social media: not only is it a low- to no-cost online marketing channel, but the heart of social media is community (hence why it's called "social"). Nothing builds support for causes better than community outreach and grassroots efforts. It's a natural fit.
Plus, according to a recent Donor Pulse(R) poll, 52% of donors say it's important for charitable organizations and non-profits to communicate with their supporters using social media, and 51% of those are higher level donors.
I'm currently working with an awesome charitable organization, writing new copy for their website and consulting with them on content and social media strategy. They collect disused cell phones, recycle them, and give proceeds to The Leukemia & Lymphoma Society. This is the first charitable organization I've worked with, and I must say - it's sparked so many ideas for using social media to build online donor communities.
Here are some of my ideas (note - these assume you already have a blog, which is why I don't talk about using one here):
Get on Twitter
This is pretty much a no-brainer. Create your branded Twitter profile page, and start finding folks to follow. You can do some Twitter market research using Twitter Search, and/or find people to follow using a directory like Twellow. Set up your RSS feeds on Twitterfeed...but don't forget to get involved in the conversations of those you follow in addition to tweeting your new blog posts. This is crucial to getting others to rally behind your cause.
Build a Ning Community
Using Ning, you can build a free online community with groups, forums to discuss relevant topics, an events page, and a page to post photos. You can brand your Ning community page with your logo and colors, add RSS feeds to your organization's blog, allow members to post meetups for local drives, and add links to donate via Paypal. You can even create badges for members to put on their own websites.
Here's a great example from the Parents of the Our Milk Money Organization.
Build a Facebook Page
I've just started using Facebook, and I'm starting to see the value it can bring to a non-profit or charitable organization. Create profiles for the officers, directors, or administrators of your organization, then create one or more groups as you see fit (business donors, individual donors, etc.). Get your developer involved and build an application for other Facebook members to post on their profiles - this could include event listings, RSS feeds, and (of course) a link to donate.
Check out this LiSA08 (Lessons in Social Advertising) Facebook application:
The downside to using Facebook is that you can't look at a Facebook page if you're not logged in or already a registered user - which creates a temporary blockade for those who aren't on Facebook. My recommendation would be to create both Facebook and a Ning community - and make sure that you link to both options from your website and/or blog.
I'm sure there are so many ways to build online donor communities using social media - these are just a few. Do you have any ideas? Please comment below!