All,
  I am trying to install ROS under OSX, but I am having some problems with the python version. I followed the instructions from the installation for OSX and I now have python 2.5 as the default, but when I try to use easy_install to get rosinstall, it seems to place rosinstall in the 2.6 directories and when I run rosinstall it searches for yaml in the 2.6 directories. Here is my output:

cmansley-macbook:~ cmansley$ which python
/opt/local/bin/python
cmansley-macbook:~ cmansley$ python --version
Python 2.5.5
cmansley-macbook:~ cmansley$ sudo easy_install -U rosinstall
Password:
Searching for rosinstall
Reading http://pypi.python.org/simple/rosinstall/
Reading http://www.ros.org/wiki/rosinstall
Best match: rosinstall 0.5.6
Downloading http://pypi.python.org/packages/source/r/rosinstall/rosinstall-0.5.6.tar.gz#md5=00556d75f290b1ef67bd22fd720de4ee
Processing rosinstall-0.5.6.tar.gz
Running rosinstall-0.5.6/setup.py -q bdist_egg --dist-dir /tmp/easy_install-0gR4EY/rosinstall-0.5.6/egg-dist-tmp-N1xgJv
zip_safe flag not set; analyzing archive contents...
Adding rosinstall 0.5.6 to easy-install.pth file
Installing rosinstall script to /usr/local/bin

Installed /Library/Python/2.6/site-packages/rosinstall-0.5.6-py2.6.egg
Processing dependencies for rosinstall
Finished processing dependencies for rosinstall
cmansley-macbook:~ cmansley$ rosinstall ~/ros http://ros.org/rosinstalls/cturtle_base.rosinstall
Traceback (most recent call last):
  File "/usr/local/bin/rosinstall", line 5, in <module>
    pkg_resources.run_script('rosinstall==0.5.6', 'rosinstall')
  File "/System/Library/Frameworks/Python.framework/Versions/2.6/Extras/lib/python/pkg_resources.py", line 442, in run_script
    self.require(requires)[0].run_script(script_name, ns)
  File "/System/Library/Frameworks/Python.framework/Versions/2.6/Extras/lib/python/pkg_resources.py", line 1167, in run_script
    exec script_code in namespace, namespace
  File "/Library/Python/2.6/site-packages/rosinstall-0.5.6-py2.6.egg/EGG-INFO/scripts/rosinstall", line 23, in <module>
    
ImportError: No module named yaml
cmansley-macbook:~ cmansley$ sudo port install py25-yaml
--->  Computing dependencies for py25-yaml
--->  Cleaning py25-yaml
cmansley-macbook:~ cmansley$ rosinstall ~/ros http://ros.org/rosinstalls/cturtle_base.rosinstall
Traceback (most recent call last):
  File "/usr/local/bin/rosinstall", line 5, in <module>
    pkg_resources.run_script('rosinstall==0.5.6', 'rosinstall')
  File "/System/Library/Frameworks/Python.framework/Versions/2.6/Extras/lib/python/pkg_resources.py", line 442, in run_script
    self.require(requires)[0].run_script(script_name, ns)
  File "/System/Library/Frameworks/Python.framework/Versions/2.6/Extras/lib/python/pkg_resources.py", line 1167, in run_script
    exec script_code in namespace, namespace
  File "/Library/Python/2.6/site-packages/rosinstall-0.5.6-py2.6.egg/EGG-INFO/scripts/rosinstall", line 23, in <module>
    
ImportError: No module named yaml
cmansley-macbook:~ cmansley$