This might be intersting for some people ordering in the US or Germany. I have selected the links to US and German shipping calculations. Maybe someone can add a calculator for other countries.
USPS claculator

Postip from Germany is a nice thing. It automatically selects the 10 cheapest ones and indicates the shipping time. You can also switch to 20 best or fastest. Just as an example I have seleted 5 kg from Germany to Australia.
Cheapest is DHL Postpaket International (DHL is part of German Postal Services), it takes 11-15 days but costs only 37 EURO. Lext one would be Lustpostpaket, 7-9 days at 58 EURO, and most expensive is FedEx, 3-4 days at 315!!!! EURO.
check here, you can alter the weight and country of destination