The Lawyer’s Guide to Fact Finding on the Internet is now in a second edition and is an essential resource for any private investigator or researcher serious about making full use of the Internet. The authors also produce a monthly e-newsletter ($60/year), an addendum to the book content. See the authors’ other products, including a free newsletter..
Robert Ambrogi has a strong Internet presence in the legal blogosphere. I haven’t read his book, The Essential Guide to the Best (and Worst) Legal Sites on the Web, but you can read an interview with him here.