Firefox: If you can never decide which Firefox persona is your favourite and want to rotate them like you rotate your desktop wallpaper then you're in luck. Personas Rotator swaps out your Firefox Personas just like a wallpaper changer.
If you're unfamiliar with Firefox personas you'll want to check out our previous treatment of the topic here. Essentially personas are skins for Firefox that alter its appearance from the standard grey we're all used to. If you've found lots of personas you like (or you just want to try a bunch of new ones) Personas Rotator is a Firefox extension that not only mines your favourites for its rotation but also entire categories at GetPersonas.com.
You set the categories you want — your favourites, abstract, nature, etc — and how frequently you want Personas Rotator to swap them out. We found that once an hour was a nice rate of rotation, the default of once a minute was way too frequent. Personas Rotator is free and works wherever Firefox does, make sure to install Personas Plus before installing Personas Rotator or you won't have any personas to rotate! Have a favourite tool for customising the look of Firefox? Let's hear about it in the comments.