Listmania!
GRE Prep for Phil
Kaplan GRE Exam 2005 with CDROM (Kaplan GRE Premier Program (W/CD))Kaplan GRE Exam 2005 with CDROM (Kaplan GRE Premier Program (W/CD)) by Kaplan Educational Centers
Buy used from: £1.51
This should be a good general introduction to the test. I've heard the practice tests are easier than the actual ones, though, so beware of that.
Kaplan GRE and GMAT Exams Math Workbook (Kaplan GMAT Math Workbook)Kaplan GRE and GMAT Exams Math Workbook (Kaplan GMAT Math Workbook)
Buy used from: £3.28
Since you haven't done math in a while...
GRE: Practicing to Take the General TestGRE: Practicing to Take the General Test by Educational Testing Service
Buy new: £8.80 / Used from: £3.45
Taking actual tests is probably the best way to practice. The real one isn't quite like this, though--it's computerized.
Gre: Literature in English (Practicing to Take the GRE)Gre: Literature in English (Practicing to Take the GRE)
Because, yeah, you'll have to take this one too. Although I expect you won't need to study much (any?).
Cracking the Gre Literature in English Subject TestCracking the Gre Literature in English Subject Test by Douglas McMullen
Buy used from: £13.44
And also? Get whatever free materials the ETS (company that administers the tests) offers: http://www.gre.org/