Drupal core

The next thing to do is to identify the actual bottlenecks. yslow and firebug can help you for front end performance - which are often a bigger issue in the wild, but while Drupal core can make those problems easier to solve (reverse cache support, CDN support etc.), they need real world situations to be measured in, and the actual solutions are often site specific. So here I'm going to focus on what you can find on your local development environment - and three tools, devel module, ab, and xdebug/cachegrind.

QUnit is a JavaScript unit testing framework that uses jQuery and is used for the jQuery UI testing as well as the jQuery testing suite itself. This project is for collaboration towards making a working testing framework for Drupal around the QUnit testing framework, and development will be for Drupal 7.x in the HEAD branch. Ideally, we can collaborate here and use the issue queue / etc. to get this working, and then we can start submitting patches to get this into Drupal core.