US History Resources

About.com’s Decade by Decade Links (http://history1900s.about.com/od/decadebydecade/Decade_By_Decade.htm) has a lot of great links for each decade, nicely collected in one place.
U.S. History Sites by Decade-Yahoo Directory (http://dir.yahoo.com/Arts/Humanities/History/U_S__History/By_Time_Period/20th_Century/?skw=decades+us+history) has links to sites about various events in US history, arranged by decade.
U.S. History Documents (http://www.law.ou.edu/hist/) has links to almost every historical document related to US History, arranged chronologically from early settlements to the present.
Findlaw.com: US Codes (Laws made by the US Congress) (http://www.findlaw.com/casecode/uscodes/) is a reputable site for legal professionals that will allow you to search for your Act by the official title, keyword, popular name, or even the number that the government assigned to it. This gives the "findings," which are the reasons that Congress decided it was necessary to have the law, and then the full text of the law itself. VERY technical, but useful.
GovSpot (http://www.govspot.com/) has free access to the best online government related resources. Looking for a tax form? Supreme Court case? The email address of your representatives? Look no further, it's all here.
Oyez: Supreme Court Multimedia Resource (http://www.oyez.org/) has information about Supreme Court cases and the justices. Also has some sounds and images.
National Park Service Battles of the Civil War (http://www.nps.gov/history/hps/abpp/battles/bycampgn.htm) has every major (and minor!) Civil War Battle—the name, alternate names, how many forces were engaged, how many casualties, what the end result of the battle was, and a brief (think 1-2 paragraphs) description. GREAT site!
50States.com (http://50States.com/) has everything you ever needed to know about all 50 states, and then some. A great place to start for basic information as well as trivia about all 50 states.
High School Ace's U.S. History & Government Links (http://highschoolace.com/ace/government.cfm) History, maps, presidents, government, and politics links, all nicely arranged by topic. It doesn't get easier than this to find lots of good resources all in one place!