Nilorea Library is a C library, which brings you:
-various helping macros, typedefs, logging facilities
-strings, hash tables, linked lists,
-network engine
-simple 2D/3D physics, little generic game managing system
Online API documentation
Some more If used with the Allegro 5 library:
-particle system, 2D isometric engine, 2D animation system
-dialogs and ressources manager
Usable as a monolith library or a collection of files