[This](http://git.chris-lamb.co.uk/?p=ikiwiki-wordpress-import.git) is a simple tool that generates [git-fast-import](http://www.kernel.org/pub/software/scm/git/docs/git-fast-import.html)-compatible data from a WordPress export XML file.
WordPress categories are mapped onto Ikiwiki tags. The ability to import comments is planned.
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I include a modified version of this script. This version includes the ability to write \[[!tag foo]] directives, which the original intended, but didn't actually do.