3 of the above titles are now free in the Kobo store.
Kaplan PMBR Finals: Constitutional Law
Kaplan Portable GRE Exam
Kaplan SAT Score Raising Dictionary
None of the rest have shown up yet, although I've just realized that you can filter search results to show "Free Only". Unfortunately, that brings up mostly Gutenberg and Smashwords freebies, but it's a start.