I use Decorator pattern all the time. I use https://github.com/drapergem/draper in rails. I also really like to use service objects. One thing I would like to use more is Observer pattern, but its not really used a lot in rails as far as I have seen.

A really good article to read is: http://blog.codeclimate.com/blog/2012/10/17/7-ways-to-decompose-fat-activerecord-models/

One thing you will have to remember is ruby and rails prefers composition over inheritance. 

This is probably a good article on inheritance and composition in ruby, gives you some good guidelines too: http://ruby.learncodethehardway.org/book/ex44.html