Unsw has a "hsc plus" scheme that awards up to 5 bonus points for achieving a band 4, 5 or 6 for the subjects that are somewhat relevant to the courses that you apply for (I'm sure you can find more information online)
They also offer extra points for people from disadvantaged backgrounds (including low socio-economic backgrounds, family conflict, death of a relative etc)
I think you can get a maximum of 10 points towards unsw
USYD has a similar program for disadvantaged students and they basically lower the atar requirement for most courses