I started with Sitepoint's SImply Rails 2, the main tutorial is a Digg
style application. I think this is a great start, but you will need
other books.
The Pragmattic Programmers: Agile Web Developmnet with Rails is decent
and the reference section at the back is well worth it.
You also need to get into Ruby too, you can pick up the nasics while
going through the SImply Rails 2 book, (there's a reuby section at the
start), then you should do some other tutorials.
I found playing around in the script/console was a great help in
getting used to the raltionships between models, tis is also covered
well in Simply Rails
Hope this helps