I have needed to use different revisions of the django trunk at different points in time (in testing locally a new revision before upgraded in production, or working on two different projects that deploy to two different production environments, etc).
There may be a better way, but how I have handled it pretty painlessly is by running this script:
!/bin/bash
rm -rf /[YOUR PATH]/$1
svn co -r $1 http://code.djangoproject.com/svn/django/trunk/django /[YOUR PATH]/$1
sudo rm -rf /Library/Frameworks/Python.framework/Versions/2.5/lib/python2.5/site-packages/django
sudo rm /usr/bin/django-admin
sudo ln -s /[YOUR PATH]/$1/ /Library/Frameworks/Python.framework/Versions/2.5/lib/python2.5/site-packages/django
sudo ln -s /[YOUR PATH]/$1/bin/django-admin.py /usr/bin/django-admin
echo "Switched to" $1
It takes a single parameter, a revision number.
./switch.sh 7000
I run this script from within a directory in my home directory called "django".
You will likely need to change the paths in the script above if you are not running Python 2.5 on Mac OSX. Also, remember to substitute "[YOUR PATH]" for the base location of where you want to store the django code.

Comments
Thanks for your script, I need to use multiple versions of django as well. I upgraded it a bit to put the directories in variables so it can be changed for new systems easier and also if you don't specify a revision it installs the head.
!/bin/bash
if [ -n "${1}" ]; then REV=$1 else REV=$(svn info http://code.djangoproject.com/svn/django/trunk/ | grep "Revision:" | sed 's/Revision: //') fi
DJANGOPATH=/home/tsaylor/code/django SITEPACKAGES=/usr/lib/python2.5/site-packages
rm -rf $DJANGOPATH/$REV svn co -r $REV http://code.djangoproject.com/svn/django/trunk/django $DJANGOPATH/$REV sudo rm -rf $SITEPACKAGES/django sudo rm /usr/bin/django-admin sudo ln -s $DJANGOPATH/$REV/ $SITEPACKAGES/django sudo ln -s $DJANGOPATH/$REV/bin/django-admin.py /usr/bin/django-admin echo "Switched to" $REV
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