NexusFont - Choose and manage your fonts with Nexus Font.
Font Manager - Simple font management for GTK+ desktop environments
Fonty - Simple tool for testing web fonts directly on live sites
gdipp - The gdipp project is a replacement of the Windows text render, which brings to you the effect of...
Font Viewer - Font Viewer is an application which does exactly that - it views fonts!
MacType - MacType render windows font smoothly and much more convenient to read.