Part 1: Applications
Part 2: Code Libraries/Resources

6. Smarty

Separating form from content is a holy grail in web design - it allows you to update the user interface of a website without altering how it works. You can even have different colour schemes or skins. Smarty is a template engine for PHP which forces you to separate form and content. It is easy to use, quick to master, and has good documentation.

7. jQuery (not Prototype)

Writing JavaScript can be frustrating at best. Using a JavaScript framework (there are many available) makes things quicker and easier, and they often include simple to use Ajax funcionality. The most common (thanks to Scriptaculous) is Prototype, but I prefer jQuery. It is much smaller, and has similar effects to Scriptaculous (although, admittedly, not as many). It also (I think) has a more logical structure.

8. WYMeditor

WYSIWYG text editors are the scourge of web developers. They often create hideous code and don't work properly, no matter what they claim, and allow users to define what their text looks like, rather than your template. Cue WYMeditor, an What-You-See-Is-What-You-MEAN editor, which creates perfectly structured XHTML code. It allows the user basic formatting tools (bold, italic etc) but not font, size, colour etc. Instead, the user chooses a style type (heading, paragraph, list etc), which can fit into your template easily.

Added to that, it works extremely well, and uses jQuery. It's brilliant!

9. Behaviour

Adding JavaScript events to HTML is as simple as CSS with the Behaviour framework. It is faster than any full JavaScript framework, and works like a charm. I use it in all my projects, and highly recommend it. The script file is small as well, especially if you pack it.

10. JavaScript Packer

If you include JavaScript files in your websites, you'll want to reduce their size as much as possible. Enter Dean Edwards' JavaScript Packer. It hugely reduces the size of JavaScript files, without losing any functionality. I love it.

That's it for now - there may be a part 3, in which I will add any new tools. I hope that someone at least has found these two useful!