You should probably look at the documentation at
as it is fairly general and a good starting point. I find the most effective way to learn, besides just dinking around in Linux yourself, is to buy a book as that way you can have Linux up on the screen in front of you and the book right beside you for quick reference. Pair this with frequent searches on Google or your Linux distributions forums and you will be well on your way to geekdom!
Just make sure you pick a good distro to start off with. I would prolly recommend Knoppix as you can run it from the CD without having to partition your hard drive. Other recommendations would be Red Hat/Fedora, Mandrake or Suse. All those distros are pretty easy to install.
When you are more comfortable with Linux I would heartily recommend you check out Debian and Gentoo.