There's not all that much to learn actually. You should be an expert with it in a couple of weeks or less. A couple of things that come to mind:
- Shortcut keys: the Command/Apple button is usually used as the Control button is on Windows keyboards. Check out this list: http://docs.info.apple.com/article.html?artnum=75459
- The minimize, maximize and close buttons are on the left and behave a little differently. Close closes the window, but the application is still loaded. You have to quit it from the menu (or Apple+Q). Maximize doesn't make a window take up the full screen space. Instead, it maximizes it to the space it needs (i.e. no scrollbars).
- If it's not enabled by default, enable the two-finger right click/scrolling on your trackpad.
That's all that comes to mind. If you run into anything specific let me know.
Cue the anti-Mac trolls.