An easy template tag for showing a breadcrumb menu on your site and on google search results with built in RDFa Markup.
I like this plugin as a standalone.
However, I am already using Yoast's WordPress SEO plugin which I realised has the same breadcrumb functionality.
Also for the semantic HTML5 folk, try something like
<nav id="breadcrumbs"> rather than a
<p> or any other inappropriate container element.
Whilst it was necessary to make a few changes in my case (purely for aesthetic reasons) this plugin works wonderfully well. For those wondering about custom post types, these are fully supported and work superbly with absolutely no configuration required.
If you are using a custom post type, make sure you have your archives set up correctly, otherwise it will be linking to a non-existent page.
I personally removed the
<p> tags from the code manually, because they are unnecessary and only proved to mess with my theme, but I could quite easily have added a new CSS rule and be done with it. For most people, this won't be a problem of course.