Concerning C, my favourite book is "The C Programming Language" by Kernighan and Ritchie. If you're looking for stuff on the internals of Linux, I haven't checked for that subject specifically, but I'm sure
The Linux Documentation Project would have something of the sort on it.
The Art of UNIX Programming should cover most of the basics of SVR4-compliant programming, and I found
this article concerning socket (network) programming in Linux from Linux Journal.