The Public Access to Legal Information Committee of the Law Librarians Association of Wisconsin has produced a wonderful guide entitled, Introduction to Legal Materials: A Manual for Non-Law Librarians in Wisconsin.
Although the primary intended audience is public librarians, the guide is useful for anyone wishing to learn more about basic materials used in federal and Wisconsin legal research.
The guide, which was published in 2003, is freely available in PDF on the Law Librarians Association of Wisconsin Web site. Bound copies are available for $10 (see Web site for details.)