USA.gov
The official government search engine, this site consolidates 20,000 government web sites and arranges them by topic, such as Money and Taxes, Healthy People and the U.S. in the World.
Data.gov
This searchable government data portal puts information generated by the executive branch of the federal government all in one place. It includes hundreds of thousands of raw data feeds from various government agencies such as the FBI, the EPA and the DoD, meaning that you no longer have to visit multiple government Web sites in search of a specific fact, update or report.
FedWorld.gov
Search U.S. Government Information Servers using the The Center for Intelligent Information Retrieval/U.S. Business Advisor govbot database. You can also search view a list of predefined searches by category.
GPO Access
Search GPO full-text databases, including the Federal Register, Congressional Bills and the U.S. Code.
SearchGov.com
Searches .gov sites. Like Google, offers caching feature.
SearchMil.com
Searches .mil sites. Also offers caching feature.