I use Blue Fox Theme 0.8 for Firefox and BloodThunder 1.0.1 for Thunderbird(email client). Instead of cluttering up my desktop with icons, I use Rocketdock 1.3.5 (seen at the bottom of image).
Installing add-ons and programs such as these can slow down your computer. Make sure you have enough resources to still enjoy your computer before using features like this. i.e. Rocketdock