I'm taking the Biology GRE in November, having graduated this past year.
For the past month or so, I studied Alberts Cell Bio, and a general biology textbook (not really comprehensive, but something). The review on Amazon.com seem to indicate that it will be pretty good for this purpose (but YMMV).
Lately, I moved to studying out of Schaum's outline of Biology, which has a great framework, but can be a bit light on the details (but probably enough to ring a bell and get you to go to your more comprehensive sources).
I took the Biochem GRE last fall, and found it really tough (It's hard to remember all the pathways and stuff). I did 'ok,' but not stellar, so I am now going for this test.