I've been using pplcruiser.co.uk for all of my exams so far and found it to be very useful. Approx 75% of the questions on the exam papers I've sat so far have been on the site so as long as you hit the books first you'll be fine. And at £4 per exam topic for 90 days access it's the only thing in aviation that is cheap!
I'd strongly recommend getting a book (I went with Pooley's), take a couple of read throughs, and then hit the exam questions.
Good luck! You'll be happy to know that the topics after you've completed Air Law are more interesting.