www.wikipedia.org
It's an online open-source encyclopaedia, it has a lot of American stuff in there which is still sort of relevant, especially when they talk about the historical basis of it in British law and they also have quite a bit of British stuff there too... even the odd bit of Australian law!
The biggest problem is you get off topic, away from the syllabus for hours and do nothing but read other law related stuff... a word of advice - DON'T GET LOST READING ABOUT THE EUROPEAN UNION! It's long, complex, huge, and extremely interesting lol
Heinemann sucks and doesn't cover some things properly, e.g. legal positivism, covered poorly. Look it up on yahoo or google and read the USYD article on it, that's really good.
What's the Maq. study guide like? I flicked through it and it looks better than Excel plus it's cheaper...