Rails 2.2 has just released. You can read the new features of this release in Rails weblog. Some highlights for the new release which are mentioned in Rails weblog are:
Rails 2.2 requires the latest RubGems version which is 1.3.1. If you haven’t upgraded yet, you can do it with the following command:
After updating RubyGems, you are ready to install the new shiny Rails 2.2
Further readings