Ruby on Rails 4
The mass assignment semantics (used with AR methods like create or update_attributes) have changed in Ruby on Rails 4. Read on to find out how to use the new interface.
Quick Rails 4 Blog Tutorial
This is quite possibly the fastest Rails tutorial you can do. All it does is get you up and running ASAP with a simple blog. It does serve to show off Rails' basic features though.
What's New in Rails 4?
Rails 4 is now officially released. While it's not a huge release (compared to Rails 3), there's still a number of new things.