If I need extra libraries for c programming, where can I find them? Is there an well organized website of the c libraries?
No known to me outside of CCAN.
The problem here is that C doesn't have any even loose specification for libraries. Compare that to e.g. packages in Java or Python or Perl.
And even then, C is quite bare bone itself leaving many things for libraries to implement themselves. I/O abstraction, memory management, multi-threading, OS integration - minor differences in how libraries work with any of the resources might make them incompatible, preventing them being used in the same project.
I have seen in past some 3rd party commercial libraries for C, covering quite a lot of functionality, but frankly I can't recommend them and honestly do not even remember their names - for they often were causing more problems than really helping. (OK, I'm lying: they were rarely causing unsolvable problems: it's the numerous workarounds which were causing often the problems later.)
Otherwise, for C you might want to check the Glib and (do not get me wrong) to also check the C standard as in my experience few actually know many of the utilities already in the standard library itself. And well, Google is your friend: lots of public domain code is there for you to simply throw as-is into your project.