No root? No problem! Obtain a copy of rubygems from ruby forge.

$ tar xzvf rubygems-1.4.2   
$ cd rubygems-1.4.2   
$ ruby setup.rb --prefix=/your/home/folder/local   
$ echo "RUBYLIB=$HOME:/same/path/as/above/lib" >> ~/.bash_profile   
$ echo "export RUBYLIB" >> ~/.bash_profile   
$ source ~/.bash_profile   

This should give you a working install of rubygems. Check out the environment

$ gem env   

Install something

$ gem install rake