Does anyone here know of a tutorial or other good resources on how to load .png files for use as textures in an OpenGL application ? I''m not interested in ready-to-use libraries or toolkits, just some plain C++ code I can tinker with. Thanks in advance.

You can write your own loader by using the PNG specifications:
http://www.w3.org/TR/REC-png.html

- Yuval

I was afraid it was going to be a bit tougher than just stealing someone else''s code. But thanks anyway =)