LinuxRaid5: Setup Linux Software RAID5! Save yourself $350! And guess what! You have much more flexibility with the RAID configuration (it's RAID on the partition level rather than on the disk level) and it's much faster than a RAID Hardware solution.
AptGet HowTo: The best tool for managing your software on your computer. Almost anything can be installed (with all dependancies) with: apt-get install package
Search: apt-cache search package
List files packages installed on system: dpkg -l *foo*
Fluxbuntu is a light-weight configured Ubuntu system that breathed new life into my Dell T450 (450Mhz PIII)!! It's a fast GUI and it works great! With all of the advantages of Ubuntu.
Fluxbox FAQ: Fluxbox is the light-weight window manager for Fluxbuntu
To add a PDF Viewer install evince: sudo apt-get install evince
I have found that install Squid Proxy install greatly speeds up the web browser (make sure and point your web browser to the proxy): sudo apt-get install squid
ScreenCasting: Multiple great ways to screen-cast in Linux
RubyProgramming: A great object oriented language that works in all platforms and can be used for both system scripts as well as web programming (Ruby On Rails). Ruby is shipped with Mac, and is a snap to install on Linux and Windows. Ruby On Rails is a fascinating way to write web programs.