While not much of a hint, for those who do not like their minimized windows taking up so much space in the Dock, now you can have them minimize into the dock icon.
Open the Dock System Preferences panel, and check the Minimize windows into application icon option. Once you do that, minimized windows will disappear into their source application's Dock icon.
If you are lazy, like me, and forgot your wireless mouse on one end of the room, and you are using a wireless keyboard on the other, it is possible to toggle this feature using Terminal. To enable this, type defaults write com.apple.dock minimize-to-application -BOOL YES, then press Return.
[robg adds: While this is documented, it's also one of the more potentially useful new features in 10.6, so I felt it worth calling out as a hint. Windows minimized into an application icon will appear with a diamond next to their names in each app's Dock contextual menu.]

