I dont know any web sights, and you have the same search engines I do, so I will share a few things I think are the most different
First off you will notice there is no right click key, to do functions that you would with the PC's right click hold down the control key while clicking.
My absolute favorite feature of the mac is if you hold down the control key, and use two fingers on the touch pad it will magnify anything(my eyes suck)
On a PC if you press enter it will launch the file, not so on a Mac. Pressing enter will rename the file. If you use key board short cuts the Apple key(the key inbetween alt and space) replaces the PC's control key for the most part. To open a file with the keyboard press Apple+O. To copy something press Apple+C, and as your probably guessing pressing Apple+V will past it.
Installing/uninstalling programs are quite different on a Mac. To install an Application you just drag it to the applications folder, and when you want to get rid of it simply drag it to the trash.
Make sure you grab VLC for the Mac if you watch/listen to much digital media
Adium is probably the best(in my opinion) messaging program
I know there is quite a bit more I am missing so if I can think of more I'll update this later, or if you have any specific questions just ask, I use both PC and Mac on a daily basis.
--------------
Mac's task bar is completly different from the PC's. When you install a program it does not automatically go to the "start menu" or "task bar"(Mac calls it the dock), instead you have to drag the application from the applications folder to the dock. To remove something from the dock just drag and drop it any where else on the screen. The only program I have ever installed that has added itself to the dock is MS Office. The trash can is also located on the dock.
Finder is the Mac's file browser. Finder is the square smily face on the dock.
If you use Vista you have probably come to love the new search on the start menu, the Mac has the same feature called spot light, it is the little blue magnifying glass in the upper right hand corner next to your clock. This nifty little program will find anything on your machine very quickly, this is my second favorite feature of the Mac(and yes I know Mac had this feature before Vista was out).
There are also widgets like Vista has, but I personally find widgets to be useless on both a Mac and PC.
It may be a wise investment to buy Parallels or VMWare Fusion(I use Fusion), as they will allow you to run Windows programs in OS X. The Mac also comes with Boot Camp, which will allow you to boot into Windows.