The bitap library is a clean implementation of regular expression (regex/grep) string matching using the bitap algorithm. Approximate (a.k.a. fuzzy) matching is allowed. This is the same algorithm as the one used in Glimpse and agrep, but it is much more complete with regard to regular expression syntax, and is much cleaner.
tkscript is a JIT-accelerated C-like scripting language with bindings for OpenGL, SDL, SDL_net, libpng, and zlib. A plugin SDK can be used to dynamically extend the script engine with custom C functions and C++ classes. It can be used to create portable, 3D, OpenGL-accelerated multimedia applications.
Parsec is a monadic parser combinator library for Haskell. It can parse context-sensitive, infinite look-ahead grammars but performs best on predictive (LL) grammars. The parser definition is in the same language as the rest of the program, so it benefits from type checking and existing development tools. Parsers are first-class values within the language and it is easy to extend the set of parsers with custom-made ones.