Hi,
I am also studying for my DAT and I picked up the DAT destroyer. It is a large test book filled with hundreds of practice questions for the 3 science sections and the quantitative reasoning section as well. I recommended it.
I also have a subscription to DATbootcamp which provides you with learning outlines and practice tests, this is a 3 month subscription, I find it very helpful.
For biology I read AP cliff notes and ferralis notes and found them rather helpful.
Lastly I purchased a Chad's video subscription from coursesaver, which I wouldn't recommend that much. He now has a free website and you should check those out instead.
For Chem/ochem - Chad's videos, boot camp, destroyer
Bio - cliff notes, ferralis notes, Barron's -available
Pat/all subjects - bootcamp
DAT destroyer - $150
Bootcamp - $120?
Chad's videos - free for now
AP cliff notes - you can find online
Ferallis - free online
I have also used a Kaplan book and a McGraw hill DAT book and found them somewhat helpful for gaining intro knowledge for subjects, but not as helpful for deeper learning. I found this at the library, so while I wouldn't pay for them I would recommend seeing what your library has.
Good luck!