A colleague has just pointed me in the direction of the IBM DeveloperWorks site <www.ibm.com/developerworks>.
They have a number of areas which they call "Technology Zones" one of which is Linux, if you go to a zone and then select Education from the left hand menu there are a number of tutorials that look interesting e.g. Introduction to XFree86 4.X, Configuring TCP/IP under Linux, Backing up your Linux machines, CVS for the developer or amateur, Getting to know GRUB, Compiling and installing software from sources, to name but a few.
You can view them online or download zipped HTML or a PDF.
You'll need to register (but what the heck, on the internet no one know you're a dog ;-) )
I've skimmed through a couple and my 1st impression is that they're useful introductory material but tend to lack a bit of detail. Probably a good starting point for someone new to a topic before getting into the more detailed stuff.
Keith ____________ BAROMETER, n. An ingenious instrument which indicates what kind of weather we are having. - Ambrose Bierce - The Devil's Dictionary