Kevin O'Keefe of LexBlog Blog put together a great of list of points to consider as part of a law firm blog policy: Law firm blog policy : Points to consider.
With "blawgs" the big issue to consider is the ethical limitations imposed on lawyer expression. Most states have vague policies on blogs, whether they constitute advertising and the implications of getting unsolicited information from clients and parties adverse to your clients.
Kevin is a great evangelist for lawyers blogging. I drank his Kool-Aid and created my own legal blog: Real Estate Space [http://realestatespace.blogspot.com].