Braver souls venture regularly into the
about:config section of Firefox, but only a few return having made any useful changes. ConfigFox promises to make the life of the casual (and determined) browser tweaker easier by providing a nice user interface and tool set for altering Firefox's internals.
Created by one Leandro Azevedo, ConfigFox comes with a bunch of pre-crafted tweaks so you can get hacking straight away. Because some changes require disabling or enabling multiple flags, ConfigFox makes sure each change is actually made, whereas if it was done manually, it's possible to miss a necessary setting or two.
ConfigFox supports profiles, so you can switch between different configurations -- great for testing -- and has some handy tools in the form of a SQLite database cleaner and profile defrag for those using regular hard drives.