Standard OS X title bars have several hidden features that can be very helpful. If you hold the command key and click the title of a window1 you will get a menu that allows you to drill down through the hierarchy to the root of the filesystem.
However, that’s not the only useful trick you can perform. If you have a document open in an application you can click on the icon in the title bar and, after holding for a brief second until the icon darkens to indicate it has been selected, drag it. This acts as a standard drag/drop but without having to go locate the file in the Finder! For example, you can save a document in TextMate, Excel, or Word and then drag/drop to Mail or Entourage and it will open a new email message with the document already attached.
One of the lesser known OS X niceties is the ability to get spelling suggestions/completions from any standard Cocoa text input. To accomplish this, simply hit the Escape key1) in any supported application (iChat, Mail, and TextEdit are some examples) and be amazed. I find this feature very useful for quickly obtaining the correct spelling of a word without taking your hands off the keyboard to get a correction. Sadly, many applications use their own text handling for various reasons so this won’t work universally (Word, TextMate, et cetera).