The following are sites I have encountered that are useful for Linux. I don't know what is the best site for Linux programming; if you know then let me know.
LinuxQuestions.org - Where newbies come for help!
Unix resources and basic instructions by Donovan Rebbechi
The Linux Documentation Project
Linux: Linux Help, Linux Forums, Linux Support, Linux Community
Linux and UNIX Resources by Bill Latura
See my Visual C++ Programmer Stuff page for more C++ stuff.