Simple breadcrumb trail for Rails. MIT license. Will likely spec and pluginize later.

application.html.erb

You are here:
<%= trail.to_html(response) %>

application_controller.rb

class ApplicationController < ActionController::Base
  before_filter :trail

  def self.trail(&block)
    # Controller-level trails become filters so they run inside the
    # request/response cycle, where internationalization etc works.
    # instance_exec means you can use path helpers.
    before_filter {|controller| controller.instance_exec(controller.send(:trail), &block) }
  end

  trail {|t| t << ['Home', '/'] }

protected

  def trail
    @breadcrumb_trail ||= BreadcrumbTrail.new
  end
  helper_method :trail

  class BreadcrumbTrail
    def initialize
      @crumbs = []
    end

    def <<(crumb)
      @crumbs << crumb
    end

    def append(crumbs)
      @crumbs += crumbs
    end

    def to_html(response)
      template = response.template
      @crumbs.map { |crumb|
        text, url = Array(crumb)
        last_crumb = @crumbs.last
        template.instance_eval {
          link_to_unless((crumb == last_crumb || url.blank?), h(text), url) {|text| content_tag(:span, text) }
        }
      }.join(" &gt; ")
    end
  end

end

items_controller.rb

class ItemsController < ApplicationController

  trail {|t| t << ['Items', '/items'] }

  def show
    trail << ['Specific item from controller', '/items/123']
  end

end

show.html.erb

<%
  trail << ['Specific item from view', '/items/123']
  # Note that since layouts are rendered after their child template,
  # trails appended in a layout will currently come after those
  # appended in the child templates.
%>