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.
XPath-based Parsing Framework (XPaF) is a simple and fast parsing framework which makes it easy to extract relations (subject-predicate-object triples) from HTML and XML documents.
A simple single site code management and package management system.
A system optimization tool.