So you want to learn Linux? The best way, the only really good way, is to get a distribution, load it on a computer and give it a try. Hope "What's the best Linux for beginners?" will help you to do this fine.
However, you may need or want to read some materials about Linux to get up to speed. My favorite book is one I've mentioned often: Robin "Roblimo" Miller's book: Point and Click Linux.
Another good book is Dee-Ann LeBlanc's Linux for Dummies, 7th Edition. Unlike Miller's book, which focuses on how to use one distribution, this is more of a general guide to no fewer than seven distributions, including Ubuntu.
If Miller's book is the blue plate special, then LeBlanc's is a taster's selection of Linux delicacies.
I would avoid most of the early editions of the Linux for Dummies series, however. Some of them are good, some are, well, not good. Besides, if you stick with the newest edition, you'll have as current a selection of Linux distributions as you can get with a print book.
However, you can also pick up a lot of Linux from resources on the web, and I don't mean trolling your way through mailing lists and FAQs. That can be useful, but it's not terribly productive unless you already have a good idea what you're looking for.
But, there are also good resources for those who don't have a clue about Linux. One of the best of them is Linuxtopia's reference library of online Linux beginners' books. These are complete books in HTML format. There is some really good stuff here, and it's not all for beginners. Linuxtopia also has more advanced books, such as an introduction to installing Xen virtualization software. All-in-all, Linuxtopia is a site that anyone who's interested in Linux should have on their browser bookmarks list.
Another handy freebie book is Version 2 of the IBM Redbook, Linux Client Migration Cookbook, which is available as a free ebook download.
IBM's Redbooks typically focus on IBM products and solutions. This book does not. It is a gift to the community. So, for everyone worried about the possibility of Windows Vista forcing a complete hardware refresh in order to upgrade from 98/ME/2000/XP, this book illustrates a path that may solve your upgrade woes, and help to fix this bug at the same time... :-)
It's not for everyone, though. To quote from the book, "Although anyone interested in using Linux on the desktop could benefit from different portions of this book, our primary audience for this book is existing business IT environments that need to begin an evaluation of desktop Linux,, or in a broader sense any organization whose strategy is to move toward greater adoption of open source software and open standards."
If that's you, though, get a copy now. You can thank me later. It's full of useful, practical information on migrating from the Windows deathtrap, umm desktop, to Linux.
One more place to look for reading materials, by the way, is DesktopLinux.com's "The Desktop Linux Book Roundup," which profiles a dozen or so recent books on desktop Linux.
Frankly, I wish I had had access to these resources back in the day when I was fumbling with Slackware floppy disks; a copy of my Unix SVR3.2 guide, which wasn't terribly helpful; and some Usenet postings. Most of you have no idea how easy you have it learning Linux today.