Social Networking and Libraries

I am giving a presentation on social networking for libraries next week (right before my last e-rate workshop, actually). I am to focus on the positives, and make social networking a less-scary, more friendly atmosphere. This is a 2-3 hour presentation for folks on every level of technology knowledge - from the accomplished techno-librarian to the not-so-confident.

I know I will cover basics, like MySpace, Flickr, and YouTube (since I have accounts on all - and they seem to be the most scary to folks), along with just the basics, like "what is social networking" and "how can I make this useful for the library."

I want to keep this light, and not bog them down with a lot of jargon, so anyone have any suggestions on other sites (I am thinking about SecondLife - but I have a vertigo issue with 3-D renditions moving around)? I am considering wikis, rss feeds and blogs, but I am not sure that would not push them over the edge. I will probably also review TSLA Learning 2.0 and CMCPL learning 2.0 and 2.1 for ideas.

Looking forward to hearing comments and suggestions!