I finished Small Pieces Loosely Joined by David Weinberger yesterday. Overall I thought it was a really interesting look at the the web. I actually think I need to go back and re-read parts of it sometime soon, since there were a lot of parts of it I agreed with. His comments about how things link together and what people are like online were perfect. One of the few times I've read something about the net and not been cringing.
Another recent book to check out is Lori Kendall's Hanging Out in the Virtual Pub: Masculinities and Relationships Online. It's either just out or due out any moment now.
