FDsys is the federal depository of government information. It contains information collected from all three branches of government.
To start your search, click here: http://www.gpo.gov/fdsys/search/home.action
Browing FDsys by topic: http://www.gpo.gov/fdsys/browse/collectiontab.action
Webinar recorded 2014 : http://icohere-meeting.net/GPOtrial/EB50DA82854F
The first video is an introduction to basic searching in the FDsys system. Topics covered include: Keyword searching, sorting results by relevance/collection/date, metadata, basic search operators such as AND/OR/NOT/BEFORE/NEAR/TRUNCATION, and full-text file types.