The ACT eBook Library is powered by OverDrive. There are a few others in Australia - you can find a list
here. None in Vic unfortunately.
Lots of universities also have digital collections (usually restricted to staff and students). Monash Uni has access to '
Ebook Library' which uses Adobe Digital Editions so should be compatible with some digital readers (or, with the help of i♥cabbages' script, any reader which supports PDFs

).