Announcing DocBook 5.0! The DocBook Technical Committee has released an official Beta 1 of DocBook 5.0, also known as DocBook:NG
The schema is maintained in RelaxNG, which is transformed into W3C schema and DTD versions. RelaxNG is much easier to work with than W3C schema, IMO.
Norm Walsh has also blogged on the 5.0 release here: http://norman.walsh.name/2005/10/28/docbook50b1
Please give 5.0 a try! The stylesheets also support DocBook 5.0, so it's almost ready for prime time! As a member of the TC, I'm very proud of the work we've accomplished here. Also, special recognition goes to Norm and Jirka for the extra efforts on this release!
See also: DocBook