Because of current fluidity of Border Crossing Information and required Documents, links to the Official Canadian and United States Sites are below.

Canadian

http://www.cbsa-asfc.gc.ca/whti-ivho/menu-eng.html

United States

http://travel.state.gov/travel/cbpmc/cbpmc_2223.html

http://www.dhs.gov/xtrvlsec/crossingborders/index.shtm