Apple / Mac OS X - Is there a Package Manager like Linux

I recommend HomeBrew - http://mxcl.github.com/homebrew/

There are two main systems for unix software on OS X: MacPorts and Fink

Fink is akin to (and iirc based on) the Debian/Ubunutu apt system: it delivers pre-compiled binaries. MacPorts is related to the older BSD Ports collections: rather than pre-built binaries, it containers pointers to the original source + patches required to make that source work on your platform (and with the other apps that you've installed via ports).

Both will get Gimp and all its dependencies installed for you - fink will be faster as it doesn't have to compile, but macports gives you more control over what gets built.

There's also a newer tool called Homebrew which I've not used; but it claims to provide better interoperability with things you've installed by hand, and rely more on the native Mac libraries instead of just the installed libraries.

A quick search shows a variety of questions already talking about Macports and Fink and differences between them.

There is MacPorts, which is a package management system for OS X that provides ports of various linux packages. Another is Fink, but MacPorts is generally more up to date.