I followed these steps when installing Ruby and Puppet (gems) on Ubuntu 10.04:
sudo su
apt-get install build-essential
apt-get install ruby rdoc libopenssl-ruby
wget http://production.cf.rubygems.org/rubygems/rubygems-1.3.7.tgz
tar zxvf rubygems-1.3.7.tgz
cd rubygems-1.3.7
ruby setup.rb
ln -s /usr/bin/gem1.8 /usr/local/bin/gem
wget http://puppetlabs.com/downloads/gems/facter-1.5.7.gem
gem install facter-1.5.7.gem
wget http://puppetlabs.com/downloads/gems/puppet-0.25.5.gem
gem install puppet-0.25.5.gem
Get the latest facter and puppet gems here
