Stands for Educational Access Scheme and it's a special scheme for students who have experienced long term educational disadvantage. Quoting from the EAS booklet (2006 booklet comes out around June): "To quality applicants must demonstrate that their educational performance during Years 11 and/or 12... has been seriously affected by circumstances beyond their control." Some examples of these disadvantages include disrupted schooling (perhaps you moved schools very often) or financial hardship (recipients of Youth Allowance are applicable here).
Different unis have different systems for successful EAS applicants. USyd, for example, allocated 500 HECS places across most courses for those students who do not meet the cutoff for their chosen course but are within five points from the HECS cutoff. It then selects the successful applicants with the highest UAI for each course until the EAS quota is filled.
Other unis have similar systems, but may allocate 5% of places to EAS students.