Google Fonts - Making the web more beautiful, fast, and open through great typography
Open Font Library - The mission of the Open Font Library is to promote your freedoms as it relates to the use of type.
Font Squirrel - Font Squirrel scours the internet in search of FREE, highest-quality, designer-friendly, commercial-use fonts and presents them for easy downloading. We don't have the most, but we do have the best.
FontsAdda.com - Collection of 15,000+ free downloadable fonts for Windows and Macintosh.
Fonts.com - Fonts.com provides the biggest and best selection of high quality desktop and web fonts. Try, buy and download classics like Helvetica, Univers, Frutiger, Trade Gothic and Avenir along with popular new fonts like Soho and Neo. Find your type!
Fonts4Free - Archive of freely downloadable fonts for Windows and Mac OS.