Saving data X platform

I'd like to know how best to organise my save game files across mac, windows and linux. All I need to do is find a place to store the user's save game data and occasional temporary files used by the game. I'm assuming that it's no longer considered correct to simply store it the application folder. I'm not concerned about accessing highscore tables across user accounts at all, I just need to know the preferred location and how to access it for each platfrom. Thanks.

XP: getenv to get the my documents folder and storing there
Vista: same
OSX: the current userfolder
Linux: the current userfolder

for all beside osx: buy grey aliens framework because at least on Vista you won't get anywhere when not understanding the basics of the OS security concept.