Bow (or libbow) is a library of C code useful for writing statistical text analysis, language modeling and information retrieval programs. The current distribution includes the library, as well as front-ends for document classification (rainbow), document retrieval (arrow) and document clustering (crossbow).
Datadec takes recursive data types modelled on those found in functional languages (Hope, Miranda, Haskell etc) and generates ANSI C code to implement them.
The MLib (pronounced "M-Lib") is a C software framework that significantly simplifies the development of highly reliable system-level libraries and programs (like daemons/services). It is small, efficient, robust and highly portable, and was designed primarily for embedded systems. (From the FreeType project)