Ning

Ning is an interesting service. I could see this being useful in a work environment (or any environment) where you need to create your own customized network. Facebook and MySpace have a lot of apps and features that are not really necessary for "serious" networking or collaboration (and could even distract from it). Ning allows a group to focus on things that are important to it, not on an outside site's standard interface.

I think all these services raise the issue of the security of data and information that's stored somewhere outside of an organization, however.