Useful Material: 

The Linux Documentation Project  ( In Particular::

  1. The Linux Cookbook

  2. Introduction to Linux - A Hands on Guide  by  Machtelt Garrels.  (PDF)

  3. Bash Guide for Beginners  by  Machtelt Garrels. (PDF)

  4. Advanced Bash-Scripting Guide by Mendel Cooper (PDF)

  5. GNU/Linux Command-Line Tools Summary by  Gareth Anderson, (PDF)

Then it can be useful to visit:

Open Source eBooks for Linux

Linux programs to replace those you run on Windows

The Time Line History of Unix ( a picture)

Other Links:

Online Linux Source code reference

Linux Source code browser at
Linux Source code Navigator

Linux shell commands cheat sheets

Useful listing of  commmads here:

Shell Scripting

A decent text on Shell Scripting here
Also consider
Or Steve Parker's

Excellent Sites for Linux Links

Linux Publications

LinuxPubs.html Slashdot, Freshmeat etc

Linux Basics

Linux Documentation Project

Installing and getting started with Linux

Linux Installation and Getting Started

On-line Linux Books 

Kernel Resources

Linux Programming Resources

Unix Programmers FAQ
Useful resourse for Linux Projects - Can get info on what happens when you fork() etc.

Beej's Guide to Network Programming
Nice tutorial on Internet Socket programming under Linux/Unix


Linux Newbie Administrator guide

A complete reference for new Linux users who wish to set up and administer their own Linux home computer, workstation and/or their home or small office network.


Links to Java and Linux resources

The Linux Programmer's Guide

Online MAN pages