The new global "command+h" shortcut means that I regularly switch to the Finder without clicking on a Finder window. This often results in my being presented with a Finder window which is not active.
Not wanting to have to reach for the mouse, I wanted a keyboard shortcut that would make the frontmost finder window active. There does not appear to be a built-in shortcut for this purpose. However, I found the the following achieves the desired effect:
"command+~" (tilde) followed by "esc"
It's not rocket science but it's handy.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20020328195742467