How comes that noone seems to know and acknowledge XSH around here? It is a simple domain-specific language environment to query and manipulate XML files combining the full power of XPath and a very intuitive shell-like command interface. Everything I know now about XML and XPath I learnt with this magnificent tool.

merlyn once wrote a pretty good introduction to XSH. Since then, version 2 was released. Although I myself have not tried that yet (I still use the CPAN version XML::XSH), it is absolutely worth a try!