People who are considering Rails as a platform often ask what it's integration with tools like HTTP authentication are like, often because that's the way they're currently solving certain problems. Up till now HTTP authentication has been something you've had to implement yourself, but now there's a plugin. Install it like so:

ruby script/plugin install http://wota.jp/svn/rails/plugins/branches/stable/htpasswd

And use code like this in your controllers:

class AdminController < ApplicationController
  htpasswd :user=>"maiha", :pass=>"berryz"
  htpasswd :user=>"maiha", :pass=>"7Et1Y7tCawx32", :type=>:crypted
  htpasswd :user=>"maiha", :pass=>"berryz", :realm=>"Member Only"
  htpasswd :file=>"/usr/local/apache/passwd/.htpasswd"
end

Neat, huh? Learn more in this interesting blog post about the plugin. Congratulations to maiha for such a useful plugin.