Seriously, buy the Alfresco Developer Guide by Jeff Potts. It has great step by step examples that will help you learn Alfresco as quickly as you can go through them. I am going through this book now and have kept notes on all the things I had to change because, for example, the latest Alfresco Community (3.3) has changed parts of its API.
Although there is a lot of useful material online, I have not found anything that beats this book as a tutorial for beginning to advanced Alfresco concepts. No I don't own stocks in either company.