Redmine 2.0.0 released
Redmine 2.0.0 drops Rails 2.3 (which is no longer maintained by the Rails team) in favour of the latest Rails 3 release, and it's now available for download at Rubyforge. New features will come with the next 2.1.0 release.
Efforts have been made to ease the upgrade of existing Redmine plugins but most of them will need a bit of work from their authors in order to be compatible with Rails 3. So if you're using some plugins, you may want to wait before switching to Redmine 2.x.