Marco has begun his promised blog series on ARIA tips! Marco, a bright new Mozilla employee is someone to listen to; he's close to the metal with respect to making accessibility work and is respected in the accessibility community.
If you are a DHTML developer you must subscribe to Marco's blog; or perish.
Oh by the way it is about time I did some other name drops. Colin Clark and I are going to be talking to John Resig and Paul Bakaus on Monday to see how we can help their community make jQuery UI rock even more with ARIA and other goodies.
We (at the ATRC) continue to help the dijit community add polish to the dojo toolkit's solid ARIA and keyboard implementation.
ARIA support is growing.