Unannotated versions of the U.S. Constitution are published in the back of Black's Law Dictionary, in West's Federal Civil Judicial Procedure and Rules, in the American Jurisprudence 2d Deskbook and many other places. Unannotated versions are posted free on Web by the National Archives, Cornell's Legal Information Institute and others.
Annotated versions of the U.S. Constitution are published as part of the United States Code Annotated and the United States Code Service (see "United States Code"). Free versions annotated with links to relevant U.S. Supreme Court cases are available on FDsys and FindLaw.
For a summary of the law concerning the various clauses of the U.S. Constitution, see Constitution of the United States of America: Analysis and Interpretation, which is often (inaccurately) referred to as the "Constitution Annotated." For a more thorough discussion, see Rotunda and Nowak's Treatise on Constitutional Law: Substance and Procedure (Thomson/West).
Ratified amendments to the U.S. Constitution are published in Black's, the USCA and USCS. They are also posted by Cornell and FindLaw.
For a general discussion of the U.S. Constitution, see Fundamentals of Legal Research (West). See also "The Other Amendments: Constitutional Amendments That Failed," 92(2) Law Library Journal 303 (Spring 2001).