Not sure if this is well known, but it surprised me ... I often drag a folder from the Finder to the browse space in a Save As dialog box, so the current folder switches to the dropped folder. However, today I accidentally dropped the folder onto the Save As text field, and noticed the that the text path of the folder was pasted there instead.
I've been using OS X forever and never spotted this. Perhaps I shouldn't be surprised, as I also routinely drag Finder items into the Terminal. This seems to apply to most Cocoa text fields that haven't had their drop behaviour changed.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20061119025037915