AAMT
Check out the Australian Association of Mathematics Teachers (AAMT). There are also some excellent AAMT Mathematics communities:
Early Years in Learning
Make it Count with Indigenous Learners
Maths in Action
Maths300
AAMT has now taken over Maths300. If you aren't already familiar with this library of rich tasks that are designed to target an array of maths skills and concepts, now is your chance to explore it! Go to www.maths300.com to view sample lessons.
NRich
For some great learning tasks, go to NRich.
ReSolve: Mathematics by Inquiry
ReSolve is a project that aims to get students and teachers thinking about and solving mathematical problems. It provides schools with high-quality, free Mathematics resources for the classroom. As it is in its start-up phase, schools can be involved in trialling some of the materials, including lessons and/or professional learning modules.
Scootle
Scootle houses the resources formerly found as part of The Learning Federation as well as new resources. There is an online community attached to Scootle. You can join and connect with teachers across the country, ask questions and share ideas. To join go to Scootle and then click on the community link. Once you join, you can search for networks to join (Maths F-10, iPad users, etc) or establish your own network.
SiMERR
SiMERR provides resources for educators, including the successful Quick Smart program.
TES Australia
TES Australia (and its parent site in the UK) contains a variety of teacher-generated resources, including resources with links to the Australian Curriculum Framework.
Top Drawer Teachers
AAMT has released Top Drawer Teachers which contains loads of resources for teachers. It comprises a series of "drawers" on topics teachers may find challenging in the Australian Mathematics Curriculum (the idea being that we keep things that we want handy in the top drawer). The contents of each drawer were written by leading groups of academics.
Other State and Territory Associations
Network of Education Associations of Tasmania: NEAT
ACT: CMA
New South Wales: MANSW
Northern Territory: MTANT
Queensland: QAMT
South Australia: MASA
Victoria: MAV
Western Australia: MAWA