Mission Control

Mission Control is an excellent tool for multi-taskers as it unifies the features of Expose and Spaces into one interface. When you activate Mission Control you see all of your desktops as well as all of your application windows from the active desktop. If you have applications open in other desktops, you can use the multitouch gesture to switch desktops and view the application windows active in each desktop. Mission Control will cascade the active windows within a single application, but sometimes the window you want is not on the top. If you move the cursor over a window and hit the space bar on the keyboard, the window will pop up above all other windows for viewing.

Even though Apple has unified most of Expose and Spaces, the option for Application Expose is still available. Application expose will only show all the windows within the active application. This can be handy when in applications like Mail where you may have multiple mail messages opened at one time.