I came across a few interesting web sites that are excellent resources if you want to improve your Linux skills:
- Tux Training is a generic resource on everything Linux. It's got some very good articles. I may contribute some of my own when I have the time;
- If you want to learn the basics of the command line and some basic bash programming, LinuxCommand.org is an excellent resource;
- If you are interested in programming, there is a good bash programming introduction at The Linux Documentation Project;
- Once you know the basics, TLDP also has an advanced bash programming guide to take you to the guru level.