Mac: Mission Control's window organisation makes it a little easier to use than previous versions of Exposé, but seeing individual windows can be hard. Here's a shortcut that can spread an app's windows out so you can focus on one of them.
Unlike Exposé, Mission Control groups together windows by app. It provides a cleaner view of everything, but sometimes you can't see the one window you want to focus. Mac OS X Hints discovers a gesture to fix this problem:
After you've entered Mission Control, move the mouse cursor over a stack of windows and scroll up. They fan out somewhat from each other, allowing you to see more of the windows' contents. Other applications and the Desktop dim.
To exit this mode, either scroll down or click off in one of the dimmed areas.
It's a simple gesture, but one that solves one of my main issues with Mission Control. Alternatively, you can also hover over a single window and hit the spacebar to see an even larger thumbnail of it.
Expand an application's windows in Mission Control [Mac OS X Hints]