Several practice driver's tests can be found online at Driving-Tests.org. This site provides free Department of Motor Vehicle permit tests of many kinds, all tailored to the laws of each state. Free practice tests are also available at DMV websites in some states.
The questions on these tests are very similar, and often identical, to those on the actual DMV test. The tests range from multiple choice to true or false and vary by topic from fines and limits to road signs to regulations and citations. The majority of the tests include about 40 or 50 questions.
Identical tests are available in Spanish. The site also provides information about getting ready for the DMV test, as well as about the next steps after preparing for and passing the test in a Frequently Asked Questions section.