I found that the best way to learn linux was to jump into it with no other option. After win2k crapped on my partition table last fall I got really fed up with it and completely removed it from my drive. I downloaded the mandrake 8.0 isos (which do not prevent you from truely learining what goes on, you can still edit the text config files if you want), bout the o'reilly "running linux" book and jumped in. It was difficult at first, as Neal Stephenson says :"Unix has a learning curve like the Matterhorn". But if you keep chipping away at it, eventually you will learn how to do everything out of necessity. If you leave yourself the wiggle room of having windows installed, you'll only end up doing things that are hard to learn how to do on the windows install.
In any case, I have found that O'reilly's "running linux" and "linux in a nutshell" are very useful.
-Hob