I found this  tutorial to be a very good introduction to ruby on rails 2.0.
I only really followed it far enough to get a working blog with comments, That next step would be to get a working many to many relationship setup for tagging. There is a lot of confusion over how todo tagging with many different gems and plugins. Since the introduction of rails 2.x there much better ways to do the many to many relationships and except in the case of tag clouds setting up tags are relatively straight forward.
This  was the best tutorial I found for setting up many to many relationships and  was very good for describing the different relationships.