The Liferay Community Wiki
is a great resource to get started. The wiki is community driven so as you're getting familiar with Liferay feel free to enhance any of the articles you find. On the Liferay.com site you'll also find the Message Boards
and additional Documentation
You may also want to consider attending a Liferay training. There are three different courses available depending on your area of focus and training is offered around the world. In fact, I was in Bangalore last month teaching the Liferay Developer course. For additional information on training, check out: http://www.liferay.com/services/training/
I would also recommend that you take a look at Liferay in Action
by Rich Sezov. The book has not been published yet, but it is currently available through the Manning Early Access Program (MEAP)
and you can download the first chapter for free to get a feel for it. Check out Rich's Blog
to keep up to day on publishing details.