Bloglines allows you to claim the feed for your blog. Verifying a claim requires adding two Bloglines provided keys to your blog, one in a post, and the other one in the template of your blog.
Adding a key to a blog post is easy enough, but the free wordpress.com account does not allow you to edit your template. No problem…just add a text widget to your blog and add the second key there.
BTW, when adding the first key in a blog post, I was only able to get it to work by including it using the code tags.
(Suggested by Jack Whitsitt, via WordPress forums. Thanks, Jack.)