Personally I think that 'real' accesisbility start in the core of an information system. And for that reason I have great hopes for future releases of the XOOPS system. The foreseen features I've seen in the dev versions as well in the X4 roadmap are very inspiring directions.
At the ELPUB 2005, the 9th ICCC International Conference on Electronic Publishing, focusing on challenges for the digital content chain, conference we've presented some notions about accessible content management systems and took XOOPS as the reference system. You can read the abstract of the paper we've submitted here: ELPUB2005:FNB
Lot of work needs to be done of course and comments/help would be appreciated.