Links to some Free Font Libraries:
 
    * The GLUT package contains routines for bitmapped and geometric fonts (made out of lines in this case).
    * glTexFont seems to be a pretty reasonable Texture-Font package.
    * The 'FNT' component of the PLIB package does a good job of rendering textured fonts - and comes with over a dozen fonts in 'TXF' format. FNT is highly portable. (Since I wrote FNT, I'm a bit biassed).
    * TexFont: this is a good tutorial on OpenGL texture-mapped text. It also uses the 'TXF' font format and contains a convertor from X-windows fonts into TXF.
    * Font3D converts fonts into geometry which can be exported into a variety of model formats.
    * GLTT relies on FreeType and can dow some amazing effects with all three font rendering mechanisms.
    * Standard Microsoft-based OpenGL's have a set of 'wgl' calls for drawing raster fonts.

AFAIK SDL has no text capabilities: you have to implement your own text-routines.
That means: yes, you must have a bitmap for at least the first ASCII characters
(ranging from 32 to about 127) and use a routine that blits them on screen
according to the text you're going to draw.