The Australian Bureau of Statistics is a rich source of information although users of the website should be aware that statistical areas and council boundaries do not necessarily match. Click here for an overview of the data collection areas.
The South West Development Commission has a wealth of useful regional data and publishes a number of useful booklets and brochures on its website.
The WA Planning Commission publishes some useful regional information which can be downloaded from their website. Of particular interest is the South West Framework, a very large file, but freely available from the WAPC.