Run a tonne of different tests much more easily. Includes validations, SEO and social rankings, mobile, spelling, network and domains, encodings, and many more. (Doesn't actually run the test, but links to online tests.)
Umbraco is an Open Source .NET based CMS. As always open source projects can teach us a lot about how things can be done properly (usually).
Here I opened one of the unit test files just to show how they do unit testing in that project. This project uses a lot of the same technologies we use. Should be helpful.
Play around with it, you might just learn something :).
Reviews a number of different tools to test browser compatibility across a tonne of different browsers. Some are web-based, others are are installed locally.
In light of the new bunch of unit testing ideas going around, thought this might be interesting.
Note: Behaviour Driven Development (BDD) is a form of TDD that attempts to involve non-technical stakeholders in the development process.
A playground for your html, css and javascript code. You can use this to create a small experimental code to test across all browsers. You can also share you code with others and work off others code (forking)
Some things we should really do: have a bug database (kudos to Melissa for doing this), daily builds, one-step build process, fix bugs before you write new code.