ARIA is a W3C standard for making complex JavaScript & AJAX-powered web apps more accessible to people with disabilities. Unlike most accessibility initiatives, this is more than just theoretical chit-chat: Firefox 2 & 3 already implement it and recently Google Reader announced an ARIA-enhanced version. John Resig has a good introduction to how it works. It's great to see movement in an area where we've almost grown used to stagnation and huge, complex, impractical recommendations (c.f. WCAG 2.0).
