Mac OS X only: Freeware application xMod tweaks OS X Leopard system settings through a easy-to-use—albeit clunky—interface. Similar to previously mentioned LeopardMOD, xMod tweaks everything from Finder to Safari, and offers tools to check the status of your hard drives or change the default screenshot behaviour. xMod is freeware, Mac OS X only. For more obscure but arguably cooler set of hidden tweaks, check out previously mentioned Secrets.