Back in the spring of 2000, I wrote MySidebar, a concoction of Mozilla sidebars, XUL and RSS. It allowed you to specify an RSS URL and would generate XUL from it and install it in Mozilla’s sidebar. (XUL involves RDF. The interconnectedness of all things, eh?)
Fozbaca recently pointed to something similar, which reminded me about the whole thing. I’ve just downloaded Mozilla 1.1, and decided to revisit the area. Things have changed – you can now plonk straight HTML into the sidebar, rather than have to use XUL. Mmmm.