So finally, rails 3.0 RC was released, cool news because rails 3.0 brings a lot of updates and it will be very fun to develop for rails 3.0. I wonder how much work would be out there migrating rails 2.x to rails 3.x versión.
Rails 3.0 RC is out just after 21 hours bunder 1.0.0.RC.1 was released, was it really a coincidence? Yeah sure…
So how to start playing with rails 3.0.RC? Pretty easy, first, install rvm, after that, lets install ruby 1.9.2 RC 2
rvm install 1.9.2
Now let’s use ruby 1.9.2
rvm 1.9.2
Then we will install bundler, because we are using rvm, we won’t use sudo at anytime
gem install bundler -v 1.0.0.rc.1
And now we can install rails rc 1
gem install rails --pre
We can start playing with rails 3.0
rails app my_app_name cd my_app_name bundle install
But finally, instead of locking your development on rails 3.0.RC 1, work with the latest version of rails that is being developed (because we will find bugs in the RC), edit the Gemfile inside your application, and do these modifications
#gem 'rails', '3.0.0.rc' # Bundle edge Rails instead: gem 'rails', :git => 'git://github.com/rails/rails.git'
Now update your app to work with the latest version of rails
bundle install
And that’s all 
You can report any bugs you find on https://rails.lighthouseapp.com/projects/8994-ruby-on-rails, and also check the bugs there, reproduce them and confirm that is really a bug or not, and don’t forget, you are also testing bundler 1.0.0.RC.1, so if you find any issue with bundler, you can report your issues on http://github.com/carlhuda/bundler/issues.
Remember, this is your opportunity to give something back to the open source community.