This is a pure-JavaScript library that detects whether Flash is blocked on the current page due to a Flash blocking extension.

Johnny Cache is a caching framework for django applications. It works with the django caching abstraction, but was developed specifically with the use of memcached in mind. Its main feature is a patch on Django’s ORM that automatically caches all reads in a consistent manner.

“CritSend ensures your email reaches its appropriate inbox and will not end up in a spam box. … Never worry about compliance, deliverability, IP reputation or blacklisting again.”

a JSLint server for more expedient linting

The z3c.jbot (or "Just a bunch of templates") package allows easy customization of existing templates and images.

Firediff is a Firebug extension that tracks changes to a pages DOM and CSS.

Uki is a fast and simple JavaScript user interface toolkit for desktop-like web applications.
It comes with a rich view-component library ranging from Slider to List and SplitPane.