This is a frequently-updated and hopefully complete index of free XML tools, with much metadata about the tools to make them easier to locate. The list below shows the various ways of accessing the information on this site.
The site contents are also available as a topic map, although this is at the moment only raw XML source. (And quite big: 880k). The form of the topic map is also experimental. Feedback is welcome. Note that you can now also browse the topic map online (see also the explanation).
If you want to learn how to use these tools you can read my book Definitive XML Application Development.
Below are various pieces of information about this site: