FreeType 2 is a high-quality and portable font engine that is capable of supporting several font formats through a simple and uniform interface. Its design is modular and allows independent "font driver" modules to be added, even at runtime, to support additional formats.

A library for rasterizing fonts. Used extensively in PfaEdit to understand the behavior of truetype fonts.

A TrueType font *rasterizer developed independently of Apple and Microsoft - by David Turner, Robert Wilhelm and Werner Lemberg. It's written in platform-independent C and therefore can be compiled for more or less any device. And it's free, with only a few minor restrictions on its use. There's a FreeType website and a mailing list.