I gave a presentation in RubyConf Argentina about what's new in Rails 4 (if you saw it please rate it). I've already posted the Rails 4 MindNode which I used to start to think about what I was going to present. The talk was in Spanish but I'm leaving here the English version of the slides.
If you want to use these slides to spread the word about what's new in Rails you don't need to ask me for permission, just feel free to use them and make the changes you want. I would appreciate a mention in your presentation and all the suggestions you may have for improving the slides and/or the mind map.
I still have to post the links I've collected of Rails 4 blog posts and commits to the Rails 4 MindNode post so keep checking it.