Here's a sampling of some of the better Internet sites devoted to U.S. military conflicts other than the Revolutionary War, Civil War and World War I. For conflicts not specifically mentioned below, see the General Online Resouces extra.

War of 1812:

U.S. Internet Genealogical Society's links to online indexes and transcriptions of War of 1812 era military records:
www.usigs.org/library/military/links/1812.htm

World War II:

World War II on the Web:
www.geocities.com/Athens/Oracle/2691/research.htm

U.S. Internet Genealogical Society's links to online indexes and transcriptions of World War II military records:
www.usigs.org/library/military/links/wwii.htm

Vietnam War:

U.S. Internet Genealogical Society's links to online indexes and transcriptions of Vietnam War military records:
www.usigs.org/library/military/links/vietnam.htm

National Archives' state-level casualty lists for the Vietnam War, sorted alphabetically by last name of casualty:
http://www.archives.gov/research_room/research_topics/pow_mia_electronic_records.html