This is such an easy time saver and I just discovered it from a beginner that I was supposed to be helping. Keeps me humble (like I needed much help – I do have children.)
I was working in Pages, the Apple word processing application and needed to get to the Fonts Window. The standard way is to select the Format Menu > Fonts > Show Fonts.
Skip all that and just select Command Key + T. Is that not cool?
Try it in any application that is an Apple application that allows you to change fonts. It worked in all the ones I use and, since I am really into the aesthetic appearance of the documents I produce and therefore spend a lot of time working with fonts, I think it is a great find.
I did qualify that this works in applications that allow you to change fonts. Jeff Gamet of The Mac Observer, in his Quick Keyboard Shortcuts column of August 4th, mentioned that using Command + T while in iCal quickly takes you back to the current date.