Exposé, a part of Mac OS X since 2003, learns some new tricks in Snow Leopard. Most notably, you can now click and hold the Dock icon for any open app in order to view all open windows for that app. This feature now extends to minimized windows--whereas in previous versions of OS X, Exposé ignored any windows that you sent to the Dock. In Snow Leopard, a thumbnail in Exposé represents each of these windows.
Also, Snow Leopard now arranges windows in a grid when you view them in Exposé. Previously, windows seemed to scale down in a haphazard fashion. I actually prefer the old method of handling Exposé: With the new Exposé arrangement, I find that all of the windows end up about the same size, which makes finding what I’m looking for more difficult, but this issue is very much a matter of personal preference.