Firefox only: If you love tweaking every aspect of Firefox with the browser's very useful
about:config feature, but you get frustrated trying to decipher cryptic configuration strings (what's a 0 or 2 mean for layout.spellcheckDefault?), Firefox extension Configuration Mania is for you.
We've mentioned Configuration Mania before, but it's just released an update and is one of those extensions worth a reminder every now and then. It's improved significantly since the last time we dedicated a post to it, and it's a great way to tweak some of the finer features of Firefox without digging into the relatively obtuse
Configuration Mania is a free download, works wherever Firefox does. The menu loads a little wonky in OS X (should work fine everywhere else), but everything still seems to work as it should. If you give it a try, let's hear what you think in the comments.
Configuration Mania [Mozilla Add-ons]