Library 2.0 Ning  is my favorite social network because it promotes serendipitous searching among people who have the same profession as well as an interest in web 2.0 in common.
I invite you to join this group of intriguing people from all over the world and add me to your friends list; see my profile .
Also, if you are a fan of serendipitous searching, check out Steve Nelson's BananaSlug , which was designed to promote serendipitous surfing.
"Directed Google searches return pages most relevant to your search term, based on the pages' popularity on the Web. You may never see some of the pages way down the list that are relevant or interesting, but off the beaten path."
Here's an example using BananaSlug. I tried "learning 2.0" and chose the Great Ideas category. The random word was time. While I found a number of the library programs with which I was familiar, the search brought me others I wouldn't have ever found by using typical search terms...e.g. a blog entry from Training Day .