NexusFont - Choose and manage your fonts with Nexus Font.
Google Fonts - Making the web more beautiful, fast, and open through great typography
Font Manager - Simple font management for GTK+ desktop environments
FontJoy - Get smart font pairings in one click
Connect Fonts Powered By Suitcase - A flexible font manager that uplevels the classic desktop application with intuitive search, pairing suggestions, and remote access in the cloud to keep you inspired, no matter where you are.
Better Google Font Finder - Sort & compare Google Fonts by their visual attributes.