Rails 3

Install Rails 3 by

$sudo gem install tzinfo builder memcache-client rack rack-test erubis mail text-format bundler thor i18n
$sudo gem install rack-mount --version=0.4.0
$sudo gem install rails --pre

and you are good to go!

Thorough Resources
http://www.rubyinside.com/rails-3-0-beta-links-2966.html

Highlights
http://guides.rails.info/3_0_release_notes.html
http://omgbloglol.com/post/344792822/the-path-to-rails-3-introduction

Some Tutorials and Guidelines
http://omgbloglol.com/post/371893012/the-path-to-rails-3-greenfielding-new-apps-with-the
http://lindsaar.net/2010/1/31/validates_rails_3_awesome_is_true
http://m.onkey.org/2010/1/22/active-record-query-interface

Upgrade
http://www.enlightsolutions.com/articles/five-ways-to-prepare-your-application-for-ruby-on-rails-3-today/
http://boldr.net/upgrade-plugins-gems-rails-3
http://github.com/rails/rails_upgrade