I have just learned from the OBA-NET (our bar member’s only online service in Oklahoma) that you can download all titles of the US Code from a website provided by the US House of Representatives. Here’s the link: http://uscode.house.gov/download/downloadPDF.shtml
According to Robert Don Gifford, an OBA member currently working in the US Attorney’s office in Reno, NV: "These are large files (up to 37MB), with each USC title occupying one or two files. They don’t correspond to any printed version, because they incorporate the materials from the supplements into the 2000 edition. This makes them more convenient for research, but less so for cite-checking."