There is a plugin out there called CommentLuv. What does this mean for SEO and looking for posts to comment on?
In Google search for "Enable CommentLuv"+ "keyword/s" to get blogs with the plugin running. You get a link as usual via the name field (use your blog), but also you get CommentLuv looking for your RSS feed and places at the bottom of the comment your last blog entry. Therefore you can get an anchor text link back to that page.
You have to hunt around for those without the nofollow attribute as usual - but it gives a neat way of finding relevant blogs and an in context link back to your blog post. Spammers would just be deleted by the owner sort of inspiring good posts in order to make use of the plugin.