Practical Rails Social Networking Sites

I'll second the votes for The Rails Way, it really is good. Another one to consider which I didn't see mentioned is an Apress book called "Practical Rails Social Networking Sites". It's slightly out of date, though anything written more than 6 months ago is. In spite of it's somewhat misleading title, it's a good introduction to building a site in Rails, and touches on most of the things you'd need to build any modern application. It serves as a good introduction to Rails IMO. One other really good resource is The Rails Guides: http://guides.rubyonrails.org - they cover everything, and are very up to date. I use them regularly.