Number2.com started as a collaboration between two graduate students, a physics professor, and a “technologist.” Although no longer owned by the quartet, the site still offers free test preparation materials. Would-be students and curious adults can register (no one under 13 without a parent) for preparatory tests for the SAT, GRE, or ACT. There is also a general Vocabulary Builder unit available after registration. Tests are adaptive and become increasingly difficult the better you do. Missed vocabulary words are remembered and repeated. The site also features tutorials, tips, and test-taking strategies to help you achieve higher results. It’s a must-see, completely free site for anyone preparing for higher education.

http://www.number2.com