You can use Automator to automate the way you use many of your Mac OS X applications without forcing you to write Apple Script code. Automator breaks common tasks into individual actions that can be linked together into a larger workflow. You can then save Automator workflows for later use; they can also be triggered at certain times of day, run when you log in, or run automatically when files are added to a folder. Automator is actually built directly into Mac OS X 10.4 "Tiger." You do not need to install the Developer packages to use it.
Interface Builder is a graphic user interface builder for Carbon and Cocoa applications. It is the main tool on Mac OS X capable of reading and writing nib files (.nib). Interface Builder integrates with Xcode to simplify the process of configuring your program's user interface.
Xcode is Mac OS X's native IDE. It provides a rich user interface for writing, building, and debugging programs, as well as for accessing online developer documentation. Xcode files are arranged into projects, containing one Xcode project file (.xcode), source code, and other resources.