If you want to know what’s new in Rails 2.1 or think that you may have missed a new feature, you should check out the e-book “Ruby on Rails 2.1. What’s new?“.
There are all new features described with an example. It’s quite amazing to see how rails evolves.
btw: did you know that there is finally an i18n patch in edge rails, to be released with rails 2.2? this is a solid foundation for other plugins to build on.