Check with your local brick and mortal stores. The major retailers like BH, Adorama, Amazon may have them because they had so many pre-orders, however a lot of the local store do have a few in stocks. This is how I got my hand on a unit a few weeks ago. Others have done the same.
I've seen two shops in Sydney with stock of the 5D3, a JBHifi and a local hole-in-the-wall printing place.
But then you have to pay AU$4200 (US$4330) for the privilege (and that's probably why they're in stock and not sold-out...)
I ordered one from www.markertek.com on Tuesday. It will be here on Friday. I've never ordered from them before but so far they have been good about getting back to me through emails. I emailed them to make sure they had it in stock before I placed my order online.
Not sure if you guys have see other threads on this but several retailers which had just received stock apparently were asked by Canon to send it back...a few members confirmed this with different retailers. Not sure if they found some issue with a specific batch of production...