In case you didn’t already know this, option-clicking the minimize button in a Finder window will collapse all open Finder windows to the Dock.

This has been the case with OS X as far back as I can remember. I can’t confirm it, but it may have been a shortcut as far back as the public preview of OS X 10.0.

With the introduction of Snow Leopard and its Cocoa-based Finder, you can maximize all Finder windows with the same shortcut.

Minimize Multiple Finder Windows to the Dock

With a Finder window as the front-most window on your desktop, hold down the option key and click the Finder window’s yellow minimize button.

All open Finder windows will be minimized to the Dock.

Expand Multiple Finder Windows

After collapsing multiple Finder windows to the Dock, you can expand them all again by holding down the option key and clicking the Dock icon for any of the collapsed Finder windows.

All of the Finder windows will expand back to the desktop.

The Small Print About This Finder Feature

Snow Leopard’s Finder can use two different methods to collapse Finder windows to the Dock. The default method is to collapse windows to the right-hand, document section of the Dock. As an alternative, you can use the Dock preference pane to enable the ‘minimize windows into application icon’ option. With this option enabled, windows you minimize will be collapsed to the icon for their respective applications.

This Finder tip only works for the default window collapse method.