There are countless presentations that give an overview of Web 2.0. Slideshare.net is an excellent site for finding reusable presentation material on Web 2.0 and almost any other topic. I ran across this one from Lee Bryant presented at LegalTech09. The reason was that generally a law practice or legal department in an enterprise often has higher levels of security around information. I wanted to see what they had to say.
Althought this was for a legal conference, just view the slides and remove the (few) references to firm and practice. It applies to any large organization. Lots of good information. Slides 9 & 10 has a good list of the types of Web 2.0 tools.
Just click on the slides to advance. Click on the FULL icon in the Slideshare frame to in full screen.