Textbook: Nature, hands down. Excellent resource which precisely explains the concepts in depth. However, like all textbooks it does have its errors and missing parts. I used Nature as my main textbook and Heinemann (which is quite detailed in some respects, yet extremely brief in others) as a supplement.
Supplementary resources: A+ Notes are excellent, Lisachem Biology 12 Student Study Guide, BioZone
Lecture Programs: TSFX. Ian Macdonnell is an excellent lecturer; he taught in such a way that it was fun to listen and you learn a heap. The notes were my main resource for study.
As I said in another thread, Andrew Douch is a brilliant teacher, and his podcasts were quite detailed and clear - the main reason I did well in biology. Listen to him on your iPod in the train - seriously. You find that in SACs and the exams his voice sometimes goes through your head.
Past Papers: STAV ones are very good, NEAP decent, LisaChem decent, TSSM atrocious. For unit 3, do VCAAs from 2006-2010 (I'd do 2006 last, it was the most difficult unit 3 paper, A+ was 72%) and for unit 4 from 1997-2010, as the course hasn't changed. The 1997-2001 papers your school may give you, or you can find on VCEnotes.
Keep an ear out for exam technique, because in Biology wording is extremely important and the examiners are pedantic.