Here are some maddest of props for two great little bits of software we've been using for RjDj work lately, and which might not be that well known yet.
Flot
Flot is a really nice little jQuery library which does exactly what it says on the box: draws charts. It strikes a very nice balance between smart, easy defaults, and being customisable.
http://code.google.com/p/flot/
South
South helps you with database migrations in Django. Database migrations are where you have made your models and deployed them live on the server, including having your SQL tables created, but now you want to change something. People who are used to the flexbility of Python find this situation frustrating. Instead of having to manually write SQL to upgrade your tables to match your new models, South will magically do the hard work for you. What's more is it will have that work represented as Python code which you can customise, modify, and version in your repository. Once again it strikes that balance between doing the right thing and being customisable.
Honorable mention
The rest of our web stack looks like this: Debian GNU/Linux, lighthttpd, python, django, lame, oggdec, postgresql, mysql, wordpress, phpbb3, boto, and we use bzr for versioning.
Together these make as nice and friendly a collection of Free Software as there ever was. Thanks, Free Software makers! You rule.