The c prototyping tools library provides generic tools for application development in plain c covering basic data structure implementations, persistence, threading and tcp and http communication. lgpl
A library of generic C modules; also, excellent list of links to similar libs
linkedlist, hashmap, pool, stack, and varray, a flexible memory allocator, CSV parser, path canonicalization routine, I18N text abstraction, configuration file module, portable semaphores, condition variables and more.