Alright so this is rather off topic (sorry mods), but does anyone in the States have any experience trying to ship a bike to Australia. USPS seemed like it would work but their size limit seems pretty impossible to fit a whole bike into. Any ideas would be greatly appreciated.

FedEx International Priority. Will get to the Australian address in approx 2-4 days. Depending on whether you have an account, cost will be a couple of hundred USD.

Not sure about sending From US to Aus but I've sent bikes from Aus to the US and Europe.
I just sent them through the post office via express courier international (EMS, trackable and insurable) so I assume they ended up going through the domestic mail system at the other end.
I picked up a bike box from my LBS and broke the bike down to suit.
The bike I sent to France had an ISP so had to end up pulling it down a little more to get it to fit (remove cranks).
The package may have been slightly oversize but as the international post was based on weight not cubic size the post office took it no problems, infact it only cost about $20 more to send the bikes half way around the world than to the other side of the country!
It helps if you use the same post office regularly and they know you.

Fedex to Oz are supposed to be great value. Had a mate who just bought a frame from the US and postage was surprisingly good value.

When you're getting price quotes be sure to establish whether the price includes clearance through customs etc. or not. This is quite expensive in Australia.