Image Magick

http://www.imagemagick.org/
http://en.wikipedia.org/wiki/Imagemagick

In Blender video productions, imagemagick will mostly be used to generate text-based image masks to use as texture images. Fortunately, imagemagick text functions are very advanced:
http://www.imagemagick.org/Usage/text/

To check the list of fonts available on your system, do:

identify -list font

identify uses the configuration file type.xml (situated at /usr/lib/ImageMagick-6.6.2/config/type.xml on my current system) as a source for the list of available fonts. If needed, the script imagick_type_gen can regenerate those configuration files.

Python bindings

Since Blender use python 3, it may sometimes be useful to be able to use imagemagick from within a python script.

It can be done this way:

import subprocess
import shlex

args={
    'bgColor':'transparent',
    'fgColor':'light slate grey',
    'fgOutlineColor':'red',
    'text':'Example',
    'size':72,
    'geometry':'350x100!',
    'output':'/tmp/out.png',
    'font':'helvetica'
    }

cmd='''convert
       xc:{bgColor!r} -resize {geometry} -gravity "Center" -font {font}
       -pointsize {size!r} -fill {fgColor!r} -stroke {fgOutlineColor!r}
       -draw "text 0,0 {text!r}" -trim {output!r}'''.format(**args)

proc=subprocess.Popen(shlex.split(cmd))
proc.communicate()

You may find the list of actual python bindings here:
http://www.imagemagick.org/script/api.php