You will find here downloads for the current version of XMCDA standard, including the XML Schema, a quick tutorial, a complete documentation, sample XMCDA files and cutomisable XSL and CSS stylesheets.
If you wish to develop your own programs respecting the XMCDA standard, please find links to XMCDA parsing libraries in various languages on the XMCDA developers page.
The latest versions for both d2 and d3 can be downloaded from sourceforge.
On the diviz download page you can find the latest version of the diviz client.