MD Net Guide has a piece on the Medical blogosphere that includes several interesting links and a great introduction to blogging:

...there comes a time in every physician's life when he or she just wants a place to tell a funny story, scream to the heavens about the frustrations of HIPAA compliance, complain about a recalcitrant patient, or otherwise blow off steam. "That's the beauty of blogs. If they want to be self-indulgent, they can," says Kevin Pho, MD (blog home: www.kevinmd.com). "This is not for business. It's for patients, but it is also for myself and other doctors, too." Dr. Pho, whose own blog is visited by some 200 readers each day, adds that "It's a way to argue and debate medical issues, whether it's the cost of practice or universal healthcare, [but] it's also just a way to keep in touch with writing"

Blogosphere is the collective term encompassing all weblogs or blogs as a community or social network. Many weblogs are densely interconnected; bloggers read others' blogs, link to them, reference them in their own writing, and post comments on each others' blogs. Because of this, the interconnected blogs have grown their own culture. Other terms in use include Blogtopia, Blogspace and Blogistan.