In fact it was quite long ago, four days after iPhone 3G was launched

http://technologyexpert.blogspot.com/2008/07/iphone-3g-unlocked-with-sim-card.html

I know the post is quite old, but just to tell you guys that there'a a way t do it!

Damn brazillians. I'll wait until WinPwn and PwnageTool can unlock 3G's, then I'll look into them