Linotype FontExplorer X is a great font manager for OSX and is completely free! You can organize your fonts using libraries, folders, tags and even smart sets in a familiar file-management like interface. update: this tool is now available for Windows. If you are a graphic designer or do any sort of design involving lots of fonts in your professional life this tool looks like it could be an incredibly valuable timesaver for you.
They put a lot of work into the graphic user interface, showing an endless variety of font styles and texts written in each style, as well as a management system for keeping your fonts organized. This application is very well done and has a free trial for 30 days.
