praystation 2,
The website for this was a little pricey, but their math and PAT sections are nearly right on what you will see on the DAT. The night before the test I exclusively went over this website for both of those sections.
I did hear that there were errors and the science sections were different, so I didn't even bother taking these practice tests.
Topscore is a MUST to get a feel for the format of the test and to get an idea how though the science sections are. The PAT on topscore is too easy. Reading is pretty close, but on the easier side.
Hope this helps.