The GMAT Club offers tests that can be accessed by selecting the "GMAT Tests" link from the home page.
The other two most popular tests in this forum are the GMAT Prep tests and Manhattan GMAT
1. GMAT Prep Tests - These test are accessed through the http://www.mba.com
website. You have to create a profile first. Then click the "Take the GMAT" link near the top of your screen. Scroll down to the bottom and you will see a section titled "GMAT Prep Products." Select the "Free GMATPrep Test-Preparation Software" link. This will provide you two tests. Uninstall and reinstall the software after you are done with Test 2 and you will get a refreshed question set.
2. Manhattan GMAT
(MGMAT) - You can get one free test at the MGMAT website (http://www.manhattangmat.com
). Create a profile. Go to the MGMAT Store and "purchase" a free test. You can also purchase additional tests from the site.
You can also try the Princeton Review
website. I haven't taken those yet though so can't vouch for the experience. Good luck!