If you want to insert the path to a file or folder into a text editor or text entry area, here's a shortcut.
Simply type the words choose file or choose folder and select those words. Then in the Services Menu, select Services -> Get Result of AppleScript (or use the very handy shortcut, Shift-Command-8). The Script Editor will launch and start bouncing on the dock. Bring it to the front, and the file or folder dialog navigation selection box will show. Navigate to the file or folder you're interested in, and click Choose.
When you do so, the full path appears in the text editor or text entry area in place of the text you originally typed and selected.
[robg adds: Since this hint uses the Services menu, it will only work in Cocoa applications, and some Carbon applications that have been coded to support Services.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20050209074043288