After seeing this question I began wondering - are there countries that say, Aussies or Kiwis (or anyone else) can get a work visa on arrival, or while in the country?
The best I've found is this:
which indicates availability of working holiday programs, but for several of them (Argentina for example) you are required to apply to Wellington (in my case) before being accepted.
Chile, on the other hand, you can't get one on arrival, but you can apply for one while being a tourist in the country.
So a chart or definitive source of countries where you can basically wander in and start working (legally) would be the ideal answer for this :D