hulk is a usable in-browser HTML editor. Running $.hulk with some options will insert a pretty JSON editor into the div with the id "selector". You can then edit the document at your leisure, in text input boxes instead of as JSON. This makes it easy for programmers and non-technical people to collaborate on configuration. Hulk is also smart about detecting your input (if it's large, use a textarea, if it looks like a number, convert it to a number, etc.).
Coronis Test is an HTML test framework based on jQuery. It is specially prepared for AJAX environments. For example, when it checks whether a given text is present, it waits some time, in case it's still processing and has not yet arrived. This way it's very easy to concentrate on actions, without waiting until something happens. It has a built-in mechanism for using action based functions, which helps when debugging something that requires repetitive tasks, like logging in or going to some specific part of the Web application as a specific user. It's a generic framework that is easy to adapt to specific needs. It also has variables that can be easily used from any part of the program.