Useful Linux Links
Cross-Referencing Linux (LXR)
This useful site that lets you browse the source code through a web interface.
Linux Documentation Project
A site whose only aim is to help you understand how Linux works
New to Linux? Want to learn more about it? Start here....
Linux Shell Scripting Tutorial
A useful tutorial for creating shell scripts in Linux
Understanding the Linux Kernel
A good book for explaining all the parts to the kernel