FTGL is a font rendering library for OpenGL applications.

FTGL is a free, open source library to enable developers to use
arbitrary fonts in their OpenGL (www.opengl.org) applications.
Unlike other OpenGL font libraries FTGL uses standard font file
formats so doesn't need a preprocessing step to convert the high
quality font data into a lesser quality, proprietary format.
FTGL uses the Freetype (www.freetype.org) font library to open and
'decode' the fonts. It then takes that output and stores it in a
format most efficient for OpenGL rendering.