Hello Chris,
I ran into the same problem yesterday when I attempted to install ROS
on my MacBook.  I solved it by doing:

$ sudo easy_install -U pyyaml

After doing that, I was able to run rosinstall.  Unfortunately, when I
tried running:

$ rosinstall ~/ros http://ros.org/rosinstalls/cturtle_pr2all.rosinstall

I got a subversion error.  I worked around that by creating (and
mounting) a disk image file which preserved the case and pointed my
rosinstall there.

Now, I'm getting the following error as I step through the tutorial:

$ rosdep install turtle_teleop rxtools
Failed to find rosdep bluez for package turtle_teleop on OS:macports
version:macports
Failed to find rosdep libbluetooth-dev for package turtle_teleop on
OS:macports version:macports
Failed to find rosdep python-bluez for package turtle_teleop on
OS:macports version:macports
Failed to find rosdep libx11-dev for package turtle_teleop on
OS:macports version:macports
Failed to find rosdep flex for package turtle_teleop on OS:macports
version:macports
Failed to find rosdep libusb for package turtle_teleop on OS:macports
version:macports
Failed to find rosdep bison for package turtle_teleop on OS:macports
version:macports
Failed to find rosdep joystick for package turtle_teleop on
OS:macports version:macports
ERROR: ABORTING: Rosdeps [u'bluez', u'libbluetooth-dev',
u'python-bluez', u'libx11-dev', u'flex', u'libusb', u'bison',
u'joystick'] could not be resolved

To me, this looks like I need to install flex, bison, and some more
packages.  Hmmm... I already have flex and bison installed (in
MacPorts), and I'm not sure that I'm going to find packages like
libusb or libbluetooth-dev in MacPorts (although I haven't tried
looking yet).

So I have 4 questions:
1) Is anybody else running ROS in MAC OS X (10.6.4)
2) If so, how did you get things to work?
3) If so, did you run through the tutorial successfully?
4) How does one search the mailing list archives?  When I plug in
something like "OS X" into the search engine at
https://code.ros.org/discuss/ros-users, I get "  No results matched
the query OS X".  Chris mentioned that OS X issues have been mentioned
previously on the list.  How would I find those?

--wpd