Just came across this in an e-mail to speed things up in the world of resources hogged by Firefox(which is still better than IE in my opinion). I noticed a big difference after doing this myself. Enjoy!
Firefox Speedup Tweak
You can speed up Firefox by defragging its database. There are a couple of add-ins to do it, but this simple method is lots quicker and doesn't require a Firefox restart. Firefox should load faster and you'll see speedier performance. In Firefox, press Control+Shift+J (or choose Tools and select Error Console). When the Firefox window opens, copy all the text in bold listed below into the Code field and click Evaluate (the button is at the end of the field). You won't see anything happen at first -- clicking Evaluate has no apparent effect. But you will notice a speedup when opening the program and browsing sites. Despite the line breaks, make sure the code below is one long line when you copy and paste it. Here is the code: