Federal Acquisition Regulations (FAR) - http://farsite.hill.af.mil/
Although the FAR is the primary rulebook for acquisition regulation, each agency may issue supplements to the FAR. To name a few:
Defense Federal Acquisition Regulations (DFAR)(201.1-253.303) http://www.acq.osd.mil/dpap/dars/dfarspgi/current/index.html
General Service Administration Acquisition Regulations (GSAR)(501.0-570.7) https://www.acquisition.gov/gsam/current/html/Part501.html
National Aeronautics Space Administration Regulations (NASFAR) http://www.hq.nasa.gov/office/procurement/regs/nfstoc.htm
Code Of Federal Regulations (CFR) and Department of Defense Grant and Agreement Regulations (DoDGARs)
The Code of Federal Regulations (CFR) is the collection of the general and permanent rules published in the Federal Register by the executive departments and agencies of the Federal Government. It is divided into 50 titles that represent broad areas subject to Federal regulation. Each volume of the CFR is updated once each calendar year and is issued on a quarterly basis.
Code of Federal Regulations (CFRs) https://www.ecfr.gov/cgi-bin/ECFR?page=browse
Code of Federal Regulations/Labor (CFRs) http://www.dol.gov/dol/cfr/
DoD Directives (DoDGARs) http://www.dtic.mil/whs/directives/
Government Forms
DOD Forms http://www.dtic.mil/whs/directives/infomgt/forms/index.htm
GSA Forms Library http://www.gsa.gov/portal/forms/type/TOP