sudo aptitude install ruby-full build-essential

wget http://rubyforge.org/frs/download.php/60718/rubygems-1.3.5.tgz
tar -xvzf rubygems-1.3.5.tgz
cd rubygems-1.3.5
sudo ruby setup.rb
sudo ln -s /usr/bin/gem1.8 /usr/bin/gem
sudo gem update --system

sudo gem install rails

rails railstest
cd railstest
ruby script/server

http://localhost:3000

You can see other versions in here:
http://rubyforge.org/frs/?group_id=126&release_id=37073