Just got my PPL by courier this week having started back in August 2010. A great feeling. Agree with what's been been posted already. My CFI recommended doing a ground exam for every five hours of flying. That way you will not have lots of exams as you head towards your cross country qualifier and skills test. I found PPLQuiz.com very good as an indicator of how much I had learned but don't be fooled into thinking you can pass the test simply by remembering the correct answers. Ensure you have understood the concepts and where necessary revise where you have got the wrong answer. I have started rereading Airplane Tech and am finding it more interesting now that I don't have an exam to pass! Good luck.