To use Tab auto-completion in Finder's 'Go to Folder...' dialog:
When manually entering a path in Finder's 'Go to Folder' dialog (located under the Go menu), pressing Tab will auto-complete the folder name if you have entered enough information to make the choice unambiguous. For instance, entering /e and pressing Tab will auto-complete to /etc/ (assuming you have no other folders beginning with "e" in the filesystem root. This is the same behavior that is seen in Terminal.
[crarko adds: I tested this, and it works as described.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20100802121918279