Graduate School in Mathematics or Statistics and the GRE Mathematics Subject Test
Follow the link below to the ETS website for general information about the GRE subject test in mathematics and a practice test you can download.
Click here for an old GRE practice exam [pdf]. This is the OLD math practice book (selected pages including practice exam). This isn't the "rescaled" test, so it is no longer distributed by ETS, but it's still the second-best practice exam for gaining experience.
Follow the link below to a free site for current and prospective math grad students, including posting of Q&A, advice and, perhaps most valuable, a self-reported listing of applicant profiles and admissions results.