Try http://www.danchisholm.net/july21/mybook/index.html for questions organised by topic. Although I found some of his questions were a bit repetitive, they hammer home the same principles tested in the exam.
You can also go to http://www.learnkey.com/custom_pages/masterExam.htm to register (free) and download a practice exam. It's very like the actual exam, with 60-odd timed questions. I was got 86% in this and got 83% in my SCJP, so they're spot on the difficulty level.