FontDoc is a dead simple program which shows you all of the fonts on your system using any text and any size you choose. Finally, no more squinting at microscopic WYSIWYG font menus or having to click on a font to see what it looks like.
FontDoc simply spits out a Rich Text document containing samples of all your fonts. Save it or print it for future reference. I'm hoping for big time-savings when I have to pick the perfect typeface for the titles in my next iMovie.
I [the developer] am also really hoping FontDoc will be rendered obsolete by something in a future version of Font Book. But until then, it's yours, dear denizens of Macdom.