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Since you are used to windows I guess one software suite you'd want is Office for Mac 2011. Get that the old one isn't that great. Otherwise a short list:

VLC player, Perian, flip4mac, aperture (get the real thing on OS X app store, it's very good value), Photoshop CS5, handbrake, steam (yes there are native games for mac now), etc.

Typically a lot of the free open sourced based programs are available for mac too. So if you were using any of them before chances are good you can find the same for mac.

Otherwise the reason why you aren't used to it is because it's UNIX under and even though they try to hide a lot of UNIXness a lot of how it works is based on UNIX ways of doing things. Mounting and unmounting disks and disk images for example.

I find typically anything you want to ask about how to use the mac it's already been asked and answered. So google when you want to know something.

Otherwise, locally here the apple store offers a complementary introduction tutorial with a real person. I never took them up on that offer because well it's not that hard to figure out plus I have friends I can just msn up when I need a quick tip. For you however, it might be a good way to go. So call your local store to see if they offer something similar.
 
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