Ning, if you haven't heard of it, is a roll-your-own "web 2.0" platform, where you can combine blogs, videos, forums, and so on in seconds in a web interface. It's like a constrained, but amazingly easy to use social content management system. What's better is that it has impressive open-source hooks in, if you want to go down that route, you can access and build upon your site's code and data structure. It's free for it's basic my community name . ning.com, and beyond that you start paying fees for custom names and services.
There's some great ning sites - I like The Our World Community which focuses on sustainable business for example. This past week has brought together a vibrant community for a different cause - Hurricane information sharing and volunteer work at https://gustav08.ning.com/, the brainchild of Andy Carvin, and it's sister site https://www.gustavwiki.com/.
These efforts also underline powerful roles for online volunteers - people unable to travel but still interested in helping out in meaningful ways, which is fantastic.