Linux Libertine is perhaps most familiar as the font used in the Wikipedia logo. This surprisingly large font family also works well with Hanyu Pinyin, though a few adjustments need to be made before all of the fonts in this family work as they should with Pinyin texts.
Here’s how those working on Linux Libertine describe it:
We work on a versatile font family. It is designed to give you an alternative for fonts like T*mes New Roman. We’re creating free software and publish our fonts under terms of the GPL and OFL. Please have a look at the paragraph concerning the license.
It is our aim to support the many western languages and provide many special characters. Our fonts cover the codepages of Western Latin, Greek, Cyrillic (with their specific enhancements), Hebrew, IPA and many more. Furthermore, typographical features such as ligatures, small capitals, different number styles, scientific symbols, etc. are implemented in this font. Linux Libertine thus contains more than 2000 characters.
All in all: Not bad.