In print, there are two commercially available versions of the U.S. Code. USCA (U.S. Code Annotated) is published by Lexis. USCS (U.S. Code Service) is published by Westlaw. To check if there have been any recent ammendments to the section you are looking at, you will need to check the U.S. Code List of Amendments that includes changes to the U.S. Code. The list will give you a brief notation of what has specifically changed and a Public Law (a recently enacted law) number. Public Laws can be read in their entirety on the Thomas Web site.
Many federal resources, including the USCA, Federal Register, and Code of Federal Regulations, are avialable on Westlaw as well as for free on the Web through the government or Cornell's Legal Information Institute.