You can install gui:config from http://guiconfig.freedig.org
So far I have created two userscripts for Greasemonkey. All of them apply to the Last.fm website.
Last.fm Reply tracker
This script adds a reply tracker to your profile page, which updates automatically. Replies you already have seen are marked as “read” and can be hidden. You also can mark threads as “spam”. Those threads will never show up in the reply tracker. Get it at userscripts.org
[This script is obsolete with the new Last.fm website]
This script removes the music player on all profile pages and replaces it with the user’s information (username, avatar, taste-o-meter, etc.). Get it at userscripts.org