Double Shot #1149

Rails 4.0: Final version released! - It's not everything I personally would have done, but certainly a great achievement and I'll be upgrading. Rails Guides are updated too.
Rails 4 on Heroku - How to do it and what you need to tweak.
RailsDiff - See the differences in generated applications between versions of Rails, so you know what you need to update.
Resources for Mac and iOS Developers - Lots and lots of links to get you started.