The one I really like is SourceCodePro. It is a mono-space font that is good for programming and the other is a sans-serif font. I really like SourceCode for programming and most mono-space font usage. I believe they accomplished their goal of every character being distinct.
The other font is SourceSansPro. It is a nice sans-serif font, but I don’t see a significant difference from existing fonts like Calibri.