Make sure you take advantage of all the free options. There are like 20 free practice tests in the big book or whatever they talk about on the GRE forum (you can download online, if you go to the forum the tests will be referenced by test and section number so everyone there is taking them). They are previous tests, but the test has somewhat outgrown the practice if you know what I'm saying. There are also some wrong answers in the key so be careful. Make sure you take the two free powerprep tests, but I would in general save those until closer to your test taking time.
For extra CATs use 800score and princeton review.
Other books are all similar and tend to give really dumb practice tests that emphasize the points they are trying to make rather than give you a real sense for the GRE, but if you have time, do more of these as well.
All this is assuming you are still taking a CAT, which I am not sure is true in 2007.