DEVELOPER LINKS
The 15 Essential UNIX commands
This is a good quick reference of the basics. It is from the website of Pete Freitag, software developer from New York. The site is worth a browse, it has a cheat sheet roundup!
Install Tomcat on Ubuntu
Very nice tutorial of getting Tomcat setup on Ubuntu. Good stuff for Java web application developers.
VI Commands
This is a very understandable reference for those who are not familiar with the VI editor, or for people like me who like to have references for commands of the VI (command line) editor.