I was in the same boat as you Achim, experienced Python guy who got
into Ruby because of Rails.  Now it's my favorite language.  I learned
on Agile Web Development and The Pickaxe, but there's definitely a lot
of the Pickaxe that I skimmed past.  The most important section for
you is probably the one on blocks.  Beyond that, you might want to run
through the section on Regular Expressions pretty quickly, as the
syntax may be a bit unfamiliar, specifically String.scan.  Play around
with rubygems and irb (equivalent to the python interactive shell). 
Oh, and a couple things that will be helpful to pick up rails quickly:

Things that begin with a colon, e.g. :action, or :controller, are
symbols, which are similar to Strings, save that they're more
efficient for certain comparison operations.  That and method calls
like has_and belongs_to_many in class definitions are actually methods
that tend to modify the class definition that they're in.

On 10/17/05, Gene Tani <gene.tani / gmail.com> wrote:
> (I knew i had a lot of links somewhere)
>
> http://pleac.sourceforge.net/
> http://martinfowler.com/bliki/CollectionClosureMethod.html
> http://onestepback.org/articles/10things
> http://www.cincomsmalltalk.com/userblogs/avi/blogView?showComments=true&entry=3284695382
> http://www.tbray.org/ongoing/When/200x/2005/08/27/Ruby
>
> BTW, Welcome to ruby, and maybe the komodo 3.5 alpha/beta for ruby can
> help
>
>
>