Mihai Parparita demonstrates how to integrate Bloglines and del.icio.us by extending Firefox to rewrite Bloglines' clip links. Now that puts me in heaven.
Serendipitously, I also found out about the greasemonkey Firefox extension, which let's you hijack the browser's internal representation of a page and modify it to your heart's content. Sort of gives you a toolbox to start doing the type of things the new Google toolbar does, except much more under your control.