Greasemonkey allows you to add scripts to modify webpages. Before we got the new site schemes here I was using one to change the site layout for instance.
LJ Ads Butler is a script to remove all the ads on LJ. It goes a bit farther than Adblock and also removes those little traces of the ads like the text that says "advertisement" and the little bits of space and bordered boxes and such that Adblock leaves behind. With this script you can't tell that there were ever ads there to begin with.