Standardized Content Area Practice Tests
Various State Tests
http://www.edinformatics.com/testing/itest.htm
This is an excellent site. It offers interactive practice tests for math, reading, science and social science at many different levels, from several different states.
California State Testing: Question Samples
http://www.cde.ca.gov/ta/tg/hs/resources.asp
http://www.edinformatics.com/testing/cal.htm
Delaware State
http://www.doe.state.de.us/aab/DSTP_items.html
Illinois State
http://electron-net.eztest.eppg.com/ISBE/