Maratus plumosus.

In the red box/ironbark/red stringy bush at Glenmaggie, Gippsland, the Plumed Peacock Spider is quite numerous. It seems to prefer to frequent the litter close to tree trunks, where it will commonly perch on fallen twigs. At this time of year, late August, it has been one of the first spiders to appear in this area of bush, with a number found. The majority have been penultimate males, with just one mature individual photographed during two outings. The photographs from various angles firstly show the former, then the mature male with the second image giving a good view of the colourful posterior flap. Click images for larger views of this tiny spider.

Further reading,
A Field Guide to Australian Spiders,
Robert Whyte and Greg Anderson.