Installing

Slackware install
Setting up wireless internet
Building the kernel
Installing the ATI driver
Installing the soundcard
Sharing files to/from Windows
Setting up the system for running Windows software
Installing a Media Player
Install Grub on a pendrive

System

Commands that are good to remember
Nano (the simplest console editor)
Setup ADSL Internet connection that requires username and password
Packages in Slackware
Directory hierarchy in Linux
Task scheduler
Remote desktop connection
List of applications I use
Firewall
Remote desktop (x11vnc)
OpenVPN
Watching movies
d-bus
ubuntu apt package management

Development

Bash Scripting
Perl Scripting
Subversion
cvs
Kiln Mercurial
Mysql on Ubuntu
Apache on Ubuntu
postgreSQL

CPP

Programming in cpp
automake
Shared libraries
Post-mortem debugging

PHP

First project
AJAX + PHP
Wordpress
snippets

Java

see here

Links

Packages

http://slackbuilds.org/
http://slackware.com/~alien/
http://slackit.wordpress.com/
http://slackware.sukkology.net/

Worth to read

http://www.linuxhq.com/guides/TLK/tlk-toc.html
http://humanreadable.nfshost.com/sdeg/index.htm
http://www.comptechdoc.org/os/linux/usersguide/index.html
http://www.linuxhaxor.net/2007/09/05/68-linux-related-free-e-books/
http://www.slackware-live.org/scripts_howto.php
http://www.linuxfromscratch.org/lfs/view/stable/index.html  

Linux equivalent of M$ applications 

CPU freq scaling, and other good scripts:

http://hellewell.homeip.net/phillip/linux/ 

good tools: powerthend(aemon), cpuspeed 

Linux compatible hardware list: https://www.fsf.org/resources/hw

New Slackware package management tool:
http://www.linux.com/feature/148826

Internationalization:
http://folk.uio.no/davidjo/i18n.php
http://www.unix.com/unix-dummies-questions-answers/17589-where-set-lang-variable.html

Great troubleshooting tips (also for X and network)
http://www.tuxradar.com/content/how-fix-most-common-linux-problems

Authentication Module in Linux (used by all system components like su and gdm and terminal and all)
http://www.tuxradar.com/content/how-pam-works