Mac: It's a cross-platform world, and if you switch between a Windows PC and a Mac frequently, you may miss Windows 7's live previews of windows from running apps in the taskbar. DockView is a Mac OS utility that adds those previews to the Mac's Dock.
Once installed, you can see at a glance how many windows of any given application are open, even if they're minimised. You can then customise the way those notifications appear. Hover over any of the running applications to see a pop-up view of all of the active windows for that program, the same way you can in Windows 7.
DockView allows you to click on any of the window previews to go straight to that window, or use hotkeys to bring that window to the front. The app is free, but will nag you to buy the paid version periodically. The full version of the app will set you back $US7.99. It supports Mac OS 10.6 and higher.