Logilab has posted XMLdiff 0.64, an open source (GPL) Python "tool that figures out the differences between two similar XML files, in the same way the diff utility does it for text files." It can be used as a library or as a command line tool. The library can operate on either XML files or DOM trees. This is at least the third tool I've necountered with the name "xmldiff". I think it's time to come up with some new names.
Dave Malcolm has posted Conglomerate 0.7.5, an open source GUI XML editor for Linux written in C, and based on libxml2 and the GTk+ and Gnome libraries. This release adds unlimited undo/redo, a Czech localization, and various small user interfac eimprovements and bug fixes. Conglomerate is published under the GPL.