Regulations for the District first appear in the D.C. Register, an online publication from the D.C. government. They are later published in the D.C. Code of Municipal Regulations, also available online. An unofficial print version of the DCMR is published by Lexis: Weil's Code of Municipal Regulations (Reserve KFD1235 .A23).
There are several good sources for administrative decisions and other executive materials. Many District of Columbia agencies post decisions on their websites, which can be accessed through a central directory posted on DC.gov. Lexis and Westlaw also host a broad collection of materials, including Board of Contract Appeals Decisions, the Office of Administrative Hearings Decisions, Insurance Bulletins and Office of Police Complaints Decisions.