What do you mean by not being eligible for uni? Is it financial or in terms of ENTER?
Anyway, if there is a financial problem, there are lots of scholarships you can get. Commonwealth Learning Scholarships (see what's offered at each uni) would probably be your best bet. Also, if you're thinking of going to Melbourne, you might like to try the Mary Jane Lewis scholarship - I think ANZ runs that one, so it's best to contact them about it. Also, there are usually other 'equity' scholarships, depending on the uni - search their individual websites. Many unis also have scholarships purely for academic excellence, which could also be an option (it's at least worth trying).
If you're worried about marks, then you probably wouldn't be eligible for a scholarship, but you could still get into uni through various 'access'-type schemes. Particularly if you go to an 'underrepresented' school, are from a rural area or have some kind of disadvantage (I'm not sure if income comes into that). Also, heaps of people take the option of going to TAFE or a low-entry score course and then transfer after a year or after they've finished their first qualification.