From time to time, I need to open a new Finder window while keeping the current window open, and while I could press Command-N, I may not want to start at the designated Finder window (set in Finder preferences).
I fiddled with the sidebar in Panther and Command-clicked on an item and, presto, a new Finder window appears.
[robg adds: This matches the behavior when command-clicking a folder in the "normal" portion of a Finder window, which has been covered here before ... nonetheless, perhaps some hadn't tried the same trick in the sidebar.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20031111083556853