- Web Content Accessibility Guidelines (WCAG) 2.0 - Level AA is a de facto standard for a solid level of web accessibility.
- The Paciello Group (TPG) - I like Steve Faulkner's focus on standards-based development, tempered with a disciplined testing approach.
- WebAIM mailing list archives - I often search the discussions, to make sure I'm not reinventing the wheel. It can be up-to-the-minute but you must test and validate whatever you read.
- Keyboard-only in one Windows browser.
- JAWS and NVDA
- IE8 and latest Firefox. I call this my "bookend strategy." If something works on both a modern standards-compliant browser and on an older but still widely used browser, then I stand a good chance of working on the stuff in the middle.
- Ignore Colors in one Windows browser. "Ignore Colors" is the IE term, but Firefox has pretty much the same thing.
- Browser zoom to 200%
- I should test more on VoiceOver, but I don't have good access to that right now.
I actually believe there is not just one single ideal list of target client technologies. But I do believe each developer needs to make a clear, rational decision about whom they're developing for. I start by trying to understand the range of disabilities my customers could have, and how those disabilities would affect their choice of technologies. Then I gather whatever data I can on disabilities and assistive technologies (ATs). Here are a couple of sources - I might or might not agree with their conclusions, but they give me their data and methodologies, so I can make my own judgments.
Yahoo's graded browser support model. Unlike Yahoo's model, targeting is not usually possible, since there is no reliable sniffing for ATs.