Q: On my Mac, using a keyboard how do I switch between windows within an application or between applications?
A: Use Expose. By default Mac OS X assigns three function keys to assist you in managing windows.
F11 - Hide all open windows.
F10 - Show all open windows of the application with focus.
F9 - Show all the open windows of all applications currently running.
Once the function key has been pressed, you can use the arrow keys to select the window of your choice.
If you have a multi-button mouse, you can also assign mouse buttons to perform the same function as the function keys.