Today, I wrote the XSLT code to add a Bloglines subscribe button to my blogs. Here's an example HTML fragment.
<a href="http://www.bloglines.com/sub/https://rssweblog.com/">
<img src="http://www.bloglines.com/images/sub_modern5.gif" alt="Subscribe with Bloglines">
</a>
Change the URL embedded in the HREF to create a subscribe button for your blog. I reverse engineered this fragment from a View Source of Steve Rubel's blog.