Check out this link: http://www.rubyinside.com/ruby-style-guides-and-tools-how-to-write-good-looking-ruby-1272.html

It highlights two useful posts about Ruby style (here and here) and includes a link to reek, a popular tool for sniffing out code smells.

UPDATE: also, check out towelie: http://gilesbowkett.blogspot.com/search?q=towelie

Really helpful screencast. You can view it here:

http://railscasts.com/episodes/133-capistrano-tasks

Seems like the launch of version 1.0 is right around the corner. sudo gem install merb and mess around with it. Full outline of the features here: http://merbist.com/2008/10/21/merb-10-rc2/

Check out the new features here http://guides.rubyonrails.org/2_2_release_notes.html

Two words: thread safety

Check out the Release Notes here: http://weblog.rubyonrails.com/2008/10/23/rails-2-1-2-security-other-fixes