The latest version of
Witch, the indispensable window-switching utility, contains a new feature that highlights minimized windows with a border color of your choosing. When you activate Witch, you'll then be able to easily see your minimized windows, as their icons will have a unique border color. (Disclaimer: I was one of at least one users who asked for this feature, as I would occasionally activate a minimized window, and wanted some way to easily see them at a glance.)
As shipped, the minimized windows are shown in the normal window hierarchy. What I wanted, though, was a way to sort of mirror the Dock's view of minimized windows -- I wanted to see all of my minimized windows grouped together. Thanks to a hidden Witch preference, you can do just that. First, disable Witch and close its System Preferences panel, then open Terminal and paste this command:
defaults write ~/Library/Application\ Support/Witch/Settings "Separate Minimized Windows" -bool true
Enable Witch again in System Preferences, minimize a few windows, then press Option-Tab and notice that all the minimized windows are listed near the end of the window list. (Any running applications without any open windows will be shown below the minimized windows.) If you'd rather get the old behavior back, disable Witch and repeat the above Terminal command, but replace
true with
false.