Where can I find more about Mozilla's accessibility initiatives?
What are some of the built-in accessibility features that are currently supported in the browser?
Firefox 3 Accessibility Features (archive.org)
Which assistive technologies support Firefox and Thunderbird?
Assistive Technology Compatibility - Documents assistive technologies for Windows, Linux, UNIX, Mac OS X and the degree of compatibility with Firefox
What can I do to make sure my Mozilla extensions are accessible?
In general, use the Accessible Toolkit Checklist (archive.org). For interface design with XUL, follow the Accessibile XUL Authoring Guidelines (archive.org).
I'm interested in helping promote the fine accessibility features that Firefox provides, what can I do?
Join the Firefox Accessibility Advocates