I had heard that it was possible to install and run Plone trunk under Python 2.6, and that it would use substantially less memory (mostly thanks to Python 2.6 improvements).  It took a bunch of fiddling and some help from David Glick, but here’s how I did it on my Mac OS X 10.5 laptop:

Install macports

Make sure /opt/local/bin is in your path.

echo 'export PATH=/opt/local/bin:$PATH' >> ~/.bash_profile

Restart terminal

(NB you may have to sudo port commands)

$ port install python26

$ port install py26-pil

if it fails, try again, second shot worked for me.  ah, ports.  

NB that you must either have an empty /usr/local or temporarily rename it to /usr/local-off while installing the port.   don't forget to name it back when you're done.  (see https://trac.macports.org/ticket/15077)

svn co https://svn.plone.org/svn/plone/buildouts/plone-coredev/trunk plone-trunk

cd plone-trunk

python2.6 bootstrap.py

python2.6 bin/buildout

bin/addzope2user user password

(to add an admin user)

bin/instance

Visit http://localhost:8080/manage_main and away you go!

To my delight, I found that it uses 62MB of RAM on startup; Plone 3.1.7/Python 2.4 uses 97MB on this machine.  That’s a pretty nice reduction.  I really hope we are able to deploy Plone 3.x under Python 2.6 soon, too!