My Debian DocBook XML packages are available through Debian.

psgmlx is psgml plus extra sgml-related packages for GNU Emacs. It's meant to provide a more user-friendly version of psgml. Installation is very easy.

I've written five SGML color themes for psgml, as add-ons to the popular color-theme package. The themes provide syntax highlighting with boldface tags in all sgml-modes.

The screenshots will give you a better idea what the themes do.