Header file information

I was wondering if anyone knew a website that would list header files and the functions they have?

There are lots of references out there. I use these a lot:
http://www.dinkumware.com/manuals/
http://www.cppreference.com/

Depends on which functions & header files you're looking for.
cppreference.com has only the standard library functions. Here are other handy references you'll probably need at some point:
http://msdn.microsoft.com/en-us/library/aa983532.aspx
http://msdn.microsoft.com/en-us/library/aa383749.aspx
http://msdn.microsoft.com/en-us/library/cscc687y.aspx
http://www.opengroup.org/onlinepubs/...idx/index.html
http://www.sgi.com/tech/stl/