http://poignantguide.net/ruby/ is one of the most entertaining writings I have read, not just out of technical books, overall. Highly recommended.

Rolling On Rails from OnLamp is a very quick and useful tutorial found here: http://www.onlamp.com/pub/a/onlamp/2005/01/20/rails.html

This is the easiest and fastest way to get started: http://tryruby.hobix.com/