Tweak Your OS X Leopard Using Secrets
Secrets is an OS X application that lets you modify you OS X Leopard easily by using a simple and easy to use preference pane in your System Preferences. You can easily browse Secrets and choose what application you want to tweak depending on what is available for the specific application you have installed in your system. Instead of using code hacks you can just click on the application you want to tweak in your preference pane and secrets will do the rest.
Secrets requires OS X 10.5 or later to run. Just double click the preference pane to install it. Use the Reload button to get the latest values from the web. You can easily revert to the default value by hitting the X button (delete key). You also have to note that before changing values for a particular application, you have to quit that application in order for the tweak to work.
The app is available for download for free and you can also share your own secrets in the community discussions. You have to note though that if you use this improperly, it can seriously harm your system, so use with precaution. You may also want to read the comments and the discussions for new updates, errors and new solutions for a safer tweaking.