Nonprofit organizations and virtual communities.
Links:
[1] http://li326-157.members.linode.com/virtual-comunities-example-sites/nonprofits/techsoup-the-technology-place-for-nonprofits
[2] http://li326-157.members.linode.com/virtual-comunities-example-sites/medical-virtual-communities/wheelchairnet
[3] http://li326-157.members.linode.com/virtual-comunities-example-sites-0