Copy the .irbrc file into your homedir, and include the Gemfile snippet into any rails project you want the tools to be available in.
Pretty much all of the ones from the irb section in the ruby-toolbox ;). Look there for more examples and docs.
>> ap Post # works on ActiveRecord model classes
>> ap Post.all # and collections
>> t Post.all # for a nice readable table
>> po Post.first # show available methods
>> ap po Post.first # show available methods and where they come from
>> Post.create :desc<TAB> # autocomplete activerecord column names, everywhere
>> {:foo => 1, :bar => 2, :boing => 3}[:bo<TAB> # complete hash keys