I've used the Bob Tait CDs - they give you a bit of variety from the practice tests in his books. Four full exams on each CD and you get 8 marking credits so you can do each exam twice before paying up again.
Only draw back is you have to print out each question in order to match the answer sheet with the questions for future reference or to figure out where you went wrong............Yes I appreciate that having easy access to this info would render the marking credits useless but I figure $50 for a CD should give you the lot.