With a few scratch builds going on at the moment I thought it'd be good to create a thread with up to date places to get timber here in Australia. I'll start with a few that I know of (but haven't necessarily dealt with), feel free to add to the list.
Local hardware stores may have suitable timber as well.
And obviously if you are doing semi-scratch builds then it goes without saying to check out Adam's collection of necks on the pitbull website.