Rails - May 2006 - Observer Subject Pattern on Rails.

Hi guys,

I''m developing a chat application with rails. I need to instantiate a 
observer for each user that logs in the app and then, when this user 
type a message update all users with the new message.

I try wiki.rubyonrails.org for help, and find nothing I can use. I 
searched using the keywords  rails observer and didn''t find anything 
interesting.

Where can I find useful documentation?

Thanks in advance.

Fernando Lujan