Hi, I made up a list of tags used in some of the glest XML configuration files, specifically I've got the tags for the tech tree, resource, unit, upgrade, faction , particle and tileset files. The descriptions of the tags aren't even nearly complete, but most of them are fairly self explanitory anyway. If you want to edit the files to make changes (or just to make them less ugly) please do, but don't let it distract you from having fun making units and stuff.
Go to
http://http://www.psdweb.org/pub/glest/ to find them.
Just so you know, I got this list by parsing through the source files, so this list of tags should be exhaustive (at least for the 1.1.0rc-1 release of the source (and for the file types specified)).
Hope this helps people with their modding.
Dan