Amarok 2.0 is supposed to be available for OS X. Refer to the Amarok 2 on OS X wiki page for details.
However, if You can't wait it is possible to get Amarok running on OS X even at Amarok's current state and no Amarok developer has ever done anything to stop you from it. The down part of the whole process is that You will be on Your own for the better part of this as it is of the moment unsupported.
You do absolutely need the Apple developer tools (Xcode) for any of these ways to work. They're a free download (after registration) from the Apple Developer Connection. I suggest you are comfortable with the terminal and do have installed the OS X BSD Subsystem installed (this is the default on OS X installation, so if you haven't turned that explicitely off it will be there).
The following approaches are supposed to work on both, PowerPC and Intel machines.
Amarok via Fink in complete
Amarok on OS X can be found in Fink's unstable repository (read Q5.8 in the Fink F.A.Q.) and can be installed via
$ fink install amarok
Be warned, while this is currently the easiest approach to get Fink running on OS X this will still result in a very lengthy compile (like 24 hours+ on a 1ghz Powerbook) - if you have not yet installed the Gnome and KDE libs that go with it. (If you are using the GStreamer engine, Fink builds a number of Gnome packages.) The upside of this is, once you got Fink up and running and tell it to build amarok with all it's dependencies, everything will take place automatically and it will require far less effort to install other Gnome and KDE based applications once you feel a desire to try them out. This is the recommended way for now as it's much less likely that you run into weird build errors than with the other approaches, and even if, there will be always people who at least will have a vague understanding what's going on - for example at the Fink beginners mailing list or in the channel #Fink on irc.freenode.org.
You will be using Apple's X11 server.
Manually compile Amarok, fill in dependencies via Fink
Of course It's still possible to compile Amarok manually which should result in a little bit more lightweight installation. You still go with Fink for some part but take only kdelibs, kdebase, kdebase-dev, libxine, libxine-shlibs from Fink's unstable repository:
$ fink install kdebase3 kdebase3-dev kdelibs3 libxine libxine-shlibs
Download the latest Amarok tarfile compile.
$ export QTDIR=/sw $ ./configure --prefix=/sw --with-qt-includes=/sw/include/qt $ make $ make all install
This has only been tested using Fink unstable.
You will be using Apple's X11 server.
Once everything is up and running but the sound stutters make sure you use esd instead of CoreAudio even if it's name sounds less cool and esd has the well-deserved reputation of being a suboptimal solution. You can further increase the audio performance during high system load by giving esd a tiny bit priority over everything else, like:
$ sudo renice -3 <process-id of esd>
You can find out esd's process-id by running 'ps ax|grep esd'. Increasing esd's priority over everything else might have unwelcomed side effects but i have not yet run into any.
If you have quit Amarok but it looks like you can't start it up again, kill all processes that belong to amarok, kill esd and
$ rm ~/.esd_auth
Now fire it back up again, it should work.
If You run Amarok and the Firefly Media Server (formerly known as mt-daapd) on the same OS X machine unexpected things might happen. If something/anything strange happens (like Your whole X server crashing when all you wanted to do was to launch Amarok...), shut down (stop) wether Amarok or Firefly and try again.
If you are interested in building yourself the lastest version of amarok, here is a good guide on how to put everything together (cmake, svn, kdelibs, qt, and Amarok) Tips on building.
A corresponding forum thread can be found here: How do I install Amarok on OS X?
As this page is currently not linked and i have no idea where such a link could be put without looking like an alien here are some keywords so it pops up in search if somebody is looking for it: Apple, Mac, Macintosh, OS X, OSX, MacOS, MacOSX, Fink, Darwinports, Darwin, Opendarwin, Xcode, Coreaudio, Jaguar, Panther, Tiger