What Font Is - Find any font from any image (commercial or free)
NexusFont - Choose and manage your fonts with Nexus Font.
FontFace ninja - A browser extension to identify and try fonts on any website
Font Viewer - Font Viewer is an application which does exactly that - it views fonts!
Fontsnatcher - Fontsnatcher helps you in identifying, testing and discovering new fonts and typefaces being used on the internet.
Font Manager - Simple font management for GTK+ desktop environments