Rails 3 comes with baked in support with bundler.
              
              Using Bundler with Rails 3
                    Install Rails as you normally would. Use sudo
                    if you would normally use sudo to install gems.
                  
                  $ gem install rails
                      We recommend using rvm for dependable Ruby
                      installations, especially if you are switching
                      between different versions of Ruby
                    
                  
                    Generate a Rails app as usual
                  
                  $ rails new myapp
$ cd myapp
                    Run the server. Bundler is transparently managing
                    your dependencies!
                  
                  $ rails server
                    Add new dependencies to your Gemfile as you
                    need them.
                  
                  gem 'nokogiri'
gem 'geokit'
                    If you want a dependency to be loaded only in
                    a certain Rails environment, place it in a group
                    named after that Rails environment
                  
                  group :test do
  gem 'rspec'
  gem 'faker'
end
                    After adding a dependency, if it is not yet
                    installed, install it
                  
                  $ bundle install
                      This will update all dependencies in your
                      Gemfile to the latest versions that do not
                      conflict with other dependencies
                    
                  
              Edit this document on GitHub if you caught an error or noticed something was missing.