I rediscovered this the other day, and thought this handy little online program deserved a mention. FontBROWSER by STC Associates is a simple program that automatically displays all the fonts you have on your system, and allows you to quickly scroll through them to see what looks best. The preview box gives a nice large visual impression of the font, and makes it easier to choose than a small menu in Illustrator, for example. A really handy tool for graphic designers.
Check it out here