GRE Resources
All of these websites pitch products for GRE preparation, but they also offer valuable information and some free preparation exercises as well.
This should be your first stop. It is the official GRE website. It contains information on all the basics, including registration, disability accommodation, preparation, and diagnostic services. Click on Test Preparation on the left-hand menu for free downloads of sample tests and test prep software.
These websites offer free practice tests:
Other sites you may find helpful: