GDom aims to provide a GObject-based API for accessing and manipulating XML documents. Most functionality will be provided by libxml2, but users will just a GNOMEy interface.
It has started as part of the 2011 Google Summer of Code.
http://git.gnome.org/browse/libgeexml/ A library implementing an API inspired by python etree.
https://gitorious.org/libgeexml-gdom A testing branch, trying to bring the above up to date and relearning some vala.
http://git.gnome.org/browse/gxml/ A library implementing an API using libxml2 using Vala.