If you're eager to learn more about concrete5, here are a few links where you can find more information about concrete5.
http://www.concrete5.org/documentation/how-tos/ provides a lot of how-tos targeted at developers, editors, as well as designers
http://www.concrete5.org/documentation/ offers you some detailed videos about various topics for editors, designers, and developers
http://www.concrete5.org/documentation/developers/ is the more technical part of the documentation aimed at developers
http://www.concrete5.org/api/ is not made for beginners but, once you know a few things about concrete5, you can find classes and methods in this API documentation
https://github.com/concrete5/concrete5 is the place where you can find the latest code changes to concrete5
http://www.concrete5.org/marketplace/addons/?filters[]=free supplies a number of free add-ons from where you can quickly get some nice examples to learn from
http://www.codeblog.ch/category/concrete5/ The author of...