The following URLs may be useful:
http://tldp.org/ - The Linux Documentation Project
http://en.wikipedia.org/wiki/FHS - The Filesystem Hierarchy Standard
http://www.gnu.org/software/bash/manual/bash.html - Bash manual
http://www.tldp.org/LDP/abs/html/ - Advanced bash scripting guide
http://www.debian.org/ - Debian home page
http://apt-get.org/ - Third-party packages for Debian


Shell features
The bash shell has several useful features for interactive use. If you press 
the up arrow key it will scroll through the command history, allowing you to 
easily repeat past commands. If you start typing a command, filename, 
environment variable etc. then press TAB, bash will attempt to complete the 
rest what you were typing. If there are multiple possibilities it will beep; 
pressing TAB again will list all the possibilities.

Shell scripting
Shell scripts (analogous to batch files under DOS) are used alot under Linux 
(and other UNIX-like operating systems). Bash is a powerful shell, with 
constructs for conditionals, looping, etc.. These are described in the bash 
man page, and also the bash manual and guide listed in my previous email.
To create a shell script, create a text file with '#!/bin/bash' on the first 
line, followed by shell commands, and give it executable permission.

To redirect the standard output stream of a command to a file, use e.g.:
$ ls -l > list.txt
To redirect standard input to a file:
$ command < file
To run two programs, with the standard output of one connected to the standard 
output of another, type the first command, the pipe symbol, then the second 
command, e.g.:
$ ls -la | less
For more information see the bash manual or guide.

For dealing with environment variables:
'export NAME=value' will set a variable, and export it so that all processes 
started from this shell will also have the variable set.
'env' will list all environment variables currently set.
'echo $HOME' will print out the contents of the environment variable called 
HOME.

Changing file permissions can be done from Konqueror, or with the command 
'chmod', 'chown', and 'chgrp'. 'rm' will delete a file, 'mv' fill rename / 
move a file. 'ln' will create symbolic or hard links (see me for an 
explanation of the difference). All these commands have man pages explaining 
how to use.

When some packages are installed, they will ask you for some options through a 
system called debconf. 'dpkg-reconfigure xyz' (where xyz is the package name) 
will allow these debconf settings for an installed package to be changed.

'mc' is a text-based file manager with built-in text editor (mcedit) and 
viewer, particularly useful when connecting via SSH.