Bob DuCharme at O'Reilly on trackback alternative, Tagbacks:

"Shelley Powers came up with an interesting alternative to trackback: "tagback," in which she creates a unique tag (in the folksonomy/flickr/del.icio.us/technorati sense of the term "tag," not the XML sense) for each weblog posting, tags the posting with that tag using Technorati's syntax, and then encourages anyone commenting on the entry (as I will once this is live) to tag their comment with the same tag. So, for example, her first post has the tag bbintroducingtagback, and the Technorati URL http://technorati.com/tag/bbintroducingtagback links to her posting and the comments on it. This way, you don't have to rely on trackback or comment software on her weblog—two processes getting more polluted by spam lately—to create a connection from her entry to yours."