Updated August 22, 2007
Thanks to data provided by Gollen, I have added support in the item editor for dozens of new magic properties, including time-relative enhancements, a few more level-based enhancements, elemental absorption, and some other odds and ends. The item editor now supports creating a much larger number of Expansion Set unique items with their full set of magic properties. See my Magic Properties page for a detailed list of properties that have been found. Most of these have been tested. (There were a few new properties referred to me that failed testing, so they have been omitted from the table.)
I've just put in a patch for adding sockets, after discovering that having too many sockets on an item could result in a scrambled display of gems, and adding too many gems can crash the whole game.
You may have noticed that this page has been shrunk down a lot. Now that the editor is usable, and I have written up some documentation for the editor, you can find most information and news about the program in the user's guide or the README and TODO files that come with the source code.
The editor was last packaged on August 2, 2003.
You can get the editor sources from here.
Since then, I have upgraded my computer to an AMD64 platform. This has necessitated some more changes in the code, since it was previously not programmed using correctly sized integer types. Sorry, but I haven't had a chance to fully test and package these changes yet.