Texcaller is a convenient interface to the TeX command line tools that handles all kinds of errors without much fuzz. It is written in plain C, is fairly portable, and has no external dependencies besides TeX.
latexmath2png is a versatile program and Python
module to allow conversion of LaTeX math equations
to PNG images. It currently supports generating
equations in the standard $...$ LaTeX math
TeXML is an XML syntax for TeX. The processor
transforms the TeXML markup into the TeX markup,
escaping special and out-of-encoding characters.
The intended audience is developers who
automatically generate [La]TeX or ConTeXt files.