The ones by Marcus Green are very good, and similar to the exam's difficulty, although the first one has some
applet questions that aren't relevant anymore. Also, Sun doesn't have as good a sense of humor.
There's also one by John Hunt with some outdated questions (like the first question for example) but which is similar to the real thing.
I think the more difficult mocks are some of the best learning experiences you can have. Try the ones by Applied Reasoning, Khalid, and the Brogden "hardest questions" applet. For links to these check
here.