Just noticed that the Weeds Australia website has been upgraded so now its very quick and simple to use, allows you to select the state, the form of weed (tree, shrub, vine etc) even the colour of the flowers produced by the weed!
http://www.weeds.org.au/weedident.htm
It also has links to two important docs I'll post them here for ease....the first details the legislation in each state, what the weed classes mean, and what should be done if a plant is identified as a weed on that list.
weednet6doc.pdf
The second is the list of weeds nationally, with columns for the class that weed has in each state it occurs
weednet6.pdf
I know that Hawaii has done an immense amount of work over the years trying to control the invasive plant pests that have been introduced to that Island. A lot of those species occur here where I am so I've made use of that data regularly.
SF