To add this breadcrumbs support, in my application www.campzero.com, a going to be online service marketplace for Bangladesh, I simply used the Crummy plugin. You can take a look at the Crummy plugin at github. It took me less than 10 minutes to find, learn and use this plugin! You can see the plugin in action at the campzero site.
I recommend this plugin for your Ruby on Rails breadcrumbs needs!