Cameron Neylon has posted Facebooks for scientists - they’re breeding like rabbits!. I really recommend reading that post. I just reproduce here some of the sites collected by him:

Sites

Blog collections: Nature Network, ScienceBlogs, Scientific Blogging, Wordpress, Blogspot, (OpenWetWare),

Social Networks: Laboratree, Ologeez, Research Gate, Epernicus, LabMeeting, Graduate Junction, (Nature Network), oh and Facebook, and Linkedin

Protocol sharing: Scivee, Bioscreencast, OpenWetWare, YouTube, lots of older ones I can’t remember at the moment

Others: Friendfeed, Twitter, GoogleDocs, GoogleGroups, Upcoming, Seesmic,

Ismael Peña has also started to collect on his wiki the some initiatives under the category Social Networking Sites for Scientists.

Finally I would like to remark the Science Blogging 2008 to be held at the Royal Institution, London, August 30, 2008.

The official forum for Science Blogging 2008, to be held at the Royal Institution, London, August 30, 2008.

The science blogging community is growing rapidly and reaching larger audiences. At Science Blogging 2008, science bloggers from around the world will have the opportunity to meet and discuss the pressing issues in science, science communication, publishing and education. What can science bloggers do to maximise their impact? Can blogging contribute to scientific research and careers? How can blogs be used to help educate the public about science? Readers and writers of science blogs, those who follow trends in online scientific communication and anyone else interested in learning more about science blogging will benefit from the discussions.