Compared to other programming languages, C is pretty devoid of fancy ways of storing data "out of the box" with just arrays, structs, pointers and function pointers (my favorite!) as the basic building blocks. It requires you to either code your own or use a 3rd party library.
So here are three different examples of open source libraries on Sourceforge.net that you might find useful. I've created a new page for them with more detail so I've just listed them briefly here.
- uthash. Makes any struct hashable by adding one field.
- Judy. Scalable dynamic sparse array with easy insert, delete, retrieve, sort, search and more facilities
- SGLIB. Simple, generic library that has linked lists, trees all accesses through simple Macros.
- Link to Hash Library List

Hi, What about an article on there use?
Wow, SGLIB made it here?
It was written by 2 of my teachers.
How did programming challenge 27 turn out?