Australian Weather Radar - Vista Sidebar Gadget
It allows you to select one of the weather radar locations provided by the Bureau of Meteorology, and then updates the image at regular intervals (10 minutes by default).
Because the sidebar is quite narrow, it also allows you re-centre the radar image so you can focus on your area of interest.
If you hover the mouse over the image, then it will cycle through the last few images (up to 10).
As outlined in the Copyright Notice on the Bureau's website, the images are copyrighted by the Commonwealth of Australia, but may be linked to without requiring permissions as long as acknowledgement is given and no advertising is nearby.