American Law Report
The American Law Reports are a widely used resource, excellent for finding a wealth of sources regarding specific legal rules or principles.
The ALR volumes also contain annotations, which are articles that "summarize the evolution of a very specific legal concept in a concise and precise fashion." The articles always include the full text of an important, relevant case, or in the more recent volumes, contain a reference to the case, reproduced later in the volume.
The articles also contain citations to the most relevant cases (always a representative sample) from throughout the United States in addition to secondary sources like law review and journal articles. However, in spite of this relative sample, the articles are not comprehensive.
On Lexis, after logging into the research page, go to:
Secondary Sources > American Law Reports (ALR)
On Westlaw, after logging into the research page, go to:
Law school tab > Secondary Legal section > American Law Reports - ALR