Google Fonts - Making the web more beautiful, fast, and open through great typography
What Font Is - Find any font from any image (commercial or free)
FontJoy - Get smart font pairings in one click
Typewolf - Typewolf helps designers choose the perfect font combination for their next design project—features web fonts in the wild, font recommendations and learning resources.
Fonts Ninja - Try fonts discovered on websites in any design software
Font Generator - Tons of font ideas in one click