In my role as software development consultant I get asked to share 'best practices'. I'm going to do myself a favor and start putting really good information in here for later use. My goal is to find practical advice for direct action; things a person or small group could just try out. No manifestos, just next steps.
My friend @devonpersing wrote an excellent article listing practical heuristics for developing accessible web applications. I believe her audience, the "Lonely Developer", is a great target. A person who wants to do good work and already has plenty queued up.
Devon has taught me a great deal about creating good products, the thing I appreciate the most is how she makes a clear case for inclusive design in development. This work is not about the blind user with a screen reader, this work is about a making your product more useful for every user. Don't leave it as a post-process.
Some heuristics here are second nature to me, I fight for standards and progressive enhancement (and lose on progressive enhancement more than I'd like). I started testing software interfaces via keyboard-only use after hearing it from Devon a while ago, it quickly exposes wackiness that does not belong. The pattern library is a great idea that I intend to use on my next web project--it always comes up but rarely gets beyond a style guide, doing accessibility work there would have great effects.