I would start here:
https://help.ubuntu.com/6.06/u...ktopguide/C/index.html
of course, that is assuming you already read over the Linux Beginner FAQ
Really the best thing to do is just install it and start using it as your primary OS. Don't keep using Windows and think you'll just dabble in Ubuntu to "learn it." The best way to learn it is to just use it exclusively. Unfortunately, this does not apply to games; if you like to game, you could check the Wine database (link in the Linux Beginner FAQ) or find free linux alternatives, or dual-boot into Windows just for that.
Anyway, the point is to use linux as your primary system and force yourself to learn the ins-and-outs, which is really quite easy if you take it one thing at a time. Another invaluable resource to me for specific little things like that is the Ubuntu guide linked in the second post of the FAQ.