Gentium ("a typeface for the nations") "is a typeface family designed to enable the diverse ethnic groups around the world who use the Latin script to produce readable, high-quality publications. It supports a wide range of Latin-based alphabets and includes glyphs that correspond to all the Latin ranges of Unicode."
It currently covers Latin and Greek ranges of Unicode 3.0. Plans are to "expand the support for Latin, Greek and Cyrillic to Unicode 4.1."
"SIL International has now embraced the Gentium project, and plans to continue development."
There are two versions of the Gentium font, regular and "GentiumAlt." GentiumAlt "is a version of the font with redesigned diacritics (flatter ones) to make it more suitable for use with stacking diacritics, and for languages such as Vietnamese. ... Since Gentium does not currently include any ‘smart’ rendering routines, there is no easy way to access these alternate diacritic shapes from within the regular Gentium font. The encoding of the fonts are the same, so the same text can be viewed with either one. There is also no problem with having both font families installed at the same time." (from the Gentium FAQ http://scripts.sil.org/Gentium_faq )
AlanWood.net description of Gentium http://www.alanwood.net/unicode/fonts.html#gentium
Wikipedia, "Gentium," http://en.wikipedia.org/wiki/Gentium