I've just uploaded my first Greasemonkey script to userscripts.org. It is called Last.fm event shoutbox feed and can be downloaded from here.
It allows to follow the conversations in Last.fm event shoutboxes easily by subscribing to feeds created for them ('out of the box' Last.fm does not provide feeds for shoutboxes, my script uses hAtom to Atom/RSS transcoder).
Below you can see how it works.
The script does not work with the new Last.fm, because the microformats were dropped during the re-design.