IxEdit

IxEdit is a JavaScript-based interaction design tool for the web. With IxEdit, designers can practice DOM-scripting without coding to change, add, move, or transform elements dynamically on your web pages. Especially, IxEdit must be useful to try various interactions rapidly in the prototyping phase of your web application.
Interactions are visual changes of the screen which occur when users act on user interface elements. In other words, interactions are the behaviors of the user interface. For instance, when a user click a button, an image switches to another, or when a user drags an edge, the viewport expands. Those are interactions. Users are doing their jobs with a computer through various interactions generally.
To implement interactions on a web page, programming with JavaScript is needed. However, it is hard to manage JavaScript for many designers. Therefore, making well-designed web interactions is difficult in general. IxEdit solves this problem. If you have basic knowledge about HTML and CSS, you can create interactions as you like. JavaScript coding is no longer needed.

http://www.ixedit.com

Jetpack

Jetpack is a newly formed experiment in using open Web technologies to enhance the browser, with the goal of allowing anyone who can build a Web site to participate in making the Web a better place to work, communicate and play.

In short, Jetpack is an API for allowing you to write Firefox add-ons using the web technologies you already know.

As with all Labs experiments, Jetpack is an open source project and everyone is welcome to participate in its design, development and testing.

Web-based

• HTML, Javascript, and CSS will be the only tools required
• Have the full power of the open Web: AJAX & multimedia capabilities including canvas, audio and video
• Streamed & accessible via a URL, just like the rest of the Web
• Debugged in the browser without restarting using common Web development tools like Firebug

Secure

• Provides access to only the privileges needed, with security issues always be presented in social-terms, and not technical-terms
• Short and easy to review code ensures that potential security issues are shallow, and review times short

Robust

• Versioned APIs so that you won't have to update & revalidate your code for every new version of Firefox
• Lightweight but full featured, enabling simple and complex applications that add to the Web experience, just like Firefox add-ons do today

Extensible

• Archiecture will allow for the easy inclusion of reviewed & versioned third-party toolkits (e.g. jQuery, Dojo, etc.) and API libraries (e.g. Twitter, Delicious, Google Maps, etc.)

https://jetpack.mozillalabs.com/

960 Gridder

960 Gridder is an excellent tool for any web developer/ designer that wants to easily align, match and/or lay out websites.

The idea came when designing a website for a student organization where I worked with several designers that handed their lay outs and designs in Photoshop format with a similar grid built-in to me. After a while I noticed how hard it became to make sure everything looked exactly how they intended it, especially in the different browsers.

960 Gridder is cross-browser compliant and works well in Internet Explorer 6/7/8, Firefox 2/3 and Chrome. Safari 4 Beta and Opera 9 is also working as expected and it should work in Safari 2.x-3.x also.

http://gridder.andreehansson.se