Unlinker

Firefox 3 Instructions:

If you're using Firefox 3 and use the link above, you'll need to change this setting before Unlinker will install.
Disable the "secure updates check": enter about:config into the address bar, right click on the page and create a new boolean value, name it extensions.checkUpdateSecurity and set it to false. Alternatively, here is a step by step video... If none of this makes sense to you, please just use the AMO link above.