I've been working on a simple accordion, and am concerned that it be accessible to those using screenReaders. Now that in itself is quite difficult because different readers behave differently, but one thing that could make it easy, is a way to easily hide/show content using something other than display:none;, which is *usually* invisible to screenreaders (reportedly if any parent div has a background image, it will become visible). Many people use tricks like positioning things way off the screen, or using the css clip property, but many of these have their own issues.
I think it would be great if there was an optional parameter in show/hide/slideUp/slideDown functions to use the most widely effective of these methods instead of show/hide.. that way for situations where certain content is hidden to streamline user's interaction, it would still be visible to screen readers, which can often have problems adjusting to dynamic content.
I've seen this plugin (
http://plugins.jquery.com/project/AccessExpander) that does this with show/hide, but not with slide and other effects and transitions (As far as I can tell, the documentation is somewhat vague). But I think for promoting accessibility etc it would be really great if something like that were built into jQuery core, just so that people don't have to put so much effort in order to make things more accessible!