Since it hasn't been mentioned yet;
- Finding blogs that are moderated and DO allow follow-able backlinks, then posting a well thought out comment on a blog post.
I try to write a comment that will have the blogger / site owner respond to the comment as well. I figure if it is a well thought out comment (and it elicits a well thought out response), then that particular blog post will 1) be better liked by google, and 2) be better liked by readers, who will (hopefully) link or FB like that page (and possibly visit my page).
I guess it isn't a whole lot different from guest blogging when you think about it...