Are you looking for a beautiful, smooth looking set of fonts to use on to your favorite operating system? Then you should definitely take a look at the Source Pro family of fonts from Adobe! The fonts are available in Serif, Sans, and Code (monospace) varieties and are free to download.
The fonts are available as separate downloads so that you can choose the ones you want to install on your system as desired or needed. Once you install the fonts, you will be able to choose from a variety of font weights for each (depending on which one you are working with).
Download the Source Serif Pro Font [SourceForge] A set of serif OpenType fonts designed to complement Source Sans Pro.
Download the Source Sans Pro Font [SourceForge] A set of OpenType fonts designed for user interfaces.
Download the Source Code Pro Font [SourceForge] A set of monospaced OpenType fonts designed for coding environments.
[via CNET News]