As announced two weeks ago a new version of Ruby on Rails has just been rolled out.
This update in mainly a maintenance release making Rails compatible with the newest version of Ruby (1.8.6).
Only two new gems has been added in this update: ruby-debug and tzinfo. ruby-debug is a command line interface for ruby-debug-base (a replacement for drb breakpointer) and tzinfo is a daylight-savings aware timezone library.
The following gems have been upgraded in the same process: actionmailer (1.3.3), actionpack (1.13.3), actionwebservice (1.2.3), activerecord (1.15.3), activesupport (1.4.2), rake (0.7.3).