Remove-it-permanently (a.k.a., properly, RIP) is a rather new firefox extension. It's a younger sibling to "nuke anything". The idea is similar - right click anything you like on webpage, choose "remove it permnentaly", and POOF, the things goes away, leaving (in most cases) just a big empty space. The change from "nuke anything", as the name implies, is that the new extension remembers the nuked elements, so that you'll never see them again! There's an options page with wildcards, so you can make your prefrences apply to a whole site.
I admit most of what you don't want to see on web pages disappears once you install AdBlock, especially if you use a good block list. Yet, RIP has allowed me to clear my favorite web sites from further useless stuff: