Good luck!
I used the Kaplan software program to prepare when I took the test 2 years ago. I liked it... it wasn't great, but there were some neat little word games and such that helped with vocab, and plenty of practice tests and practice sections.
I ended up getting such a good score on the math and verbal that I was convinced the computer had messed up somehow.
Maybe it was all the practice tests I took. My analytical writing score, however, was abysmal.. I think it was a 4 out of 6. Somehow I still got into all the grad schools I applied to.
I also had to take the Biochemistry, Cell and Molecular Biology subject test, so I may be able to provide advice if anyone is taking that one.