I love MEDLIB-L.
This article (from BMJ Careers) was mentioned today. As the poster points out, you can substitute the American database names for the British ones, and the article applies to American medical librarians as well.
A number of different types of support are on offer. A librarian is not only an information expert, able to advise on best resources, but also a trainer and a service provider. Medical librarians have good credentials, and so armed with a few tips you will be able to make better use of their help.