FedBizOpps (FBO) database (Fed Biz Ops, FedBizOps, Fed Biz Opps), formerly known as the Commerce Business Daily (CBD) lists US Government contracting opportunities.
Sites for the text of US Government contracts regulations; FAR, DFAR:
Federal Acquisition Regulation (FAR)
FARSite Contracting Laboratory, Hill AFB
Defense Procurement and Acquisition Policy For the DFARs
LII Contract From Cornell Legal Information Institute, Overview, Resources, and other tabs. Site includes Federal law, regulations and court decisions, for states the Uniform Commercial Code sections, links to international law, and other contracts sites.