WordPress.com Get’s Random
Matt Mullenweg has added his random redirect tool to WordPress.com blogs, and so if you are interested in offering people the ability to randomly float around your blog on WordPress.com, you now can.
Try adding ?random to the end of your WordPress.com URL and it will redirect you to a random post on your blog.
You can link to that address like any other, either in your post or a widget.
Check it out on the WordPress.com blog.