A Ruby implementation of the CAS client is now available at http://rubyforge.org/projects/rubycas-client/

The library is designed to easily integrate with Rails as an ActionController filter, but may be adapted for other purposes.

Documentation and example usage is available at http://rubycas-client.rubyforge.org/

The easiest way to install the client is via ruby gems, by typing the following at a shell prompt (you will probably need root access):

...

RubyCAS-Client

The library integrates directly with rails 2.3 and 3.x and can also be made to work with Sinatra and Padrino.

Rack-CAS

Rack-CAS is simple Rack middleware to perform CAS client authentication.