Behaviour is a library that makes it easy to attach code to one or more page elements using CSS selectors. That may not sound like much, but it can radically clean up your code. Good stuff!
Greasemonkey is a plugin for Firefox that “lets you to add bits of DHTML (‘user scripts’) to any webpage to change it’s behavior.” As a designer, there’s a side of me that hates the idea that someone might use CSS to make my pages look like useit.com. But as a user I love the fact that I can fix annoying UI issues, many of them small enough (or me-specific enough) that I’d never expect (or want) the “fix” to get hard-coded.
I think one of the best uses of DHTML is to provide contextual information without requiring people to open a new page. There’s a nice example of this on the hp search page, where search tips pop up like so:
You know those little Venn diagrams you’ve seen in someone’s PowerPoint presentation showing how product design needs to take into account business logic, user needs, and technical constraints? Well, here’s what happens when business logic takes precedence over user needs: Dirty Trickz for the Adult Webmaster. Probably as good a list as any of best practices to avoid.
Oh, and my last gig (which I thought was still in “soft-launch” since it’s full of typos and such, but which I see linked on xblog) was a couple of scripts for Apple’s new Internet Developer area:
dhtml pop-up menus
Of course, I tried to slip a little user-centered design evangelism into these basic cut-n-paste scripts.