I recommend Ulli Meybohms Freeware Editor "Proton" v3.2eng for Windows.
It's freeware, does not need to be installed - just unzip, start the .exe.
It can write files in UNIX format as the DOM mod files are, it's available in english and I have done a syntax scheme for it.
The scheme is still in the works, so it's quite simple up to now. If there's interest in it and I can figure out more of the syntax, I'll try to do a updated version for Dom3. Sadly documentation for the .sch files is non-existant.
I'll upload the latest version to my website in the next days, stay tuned.
hope this is helpful
A.
Update: 10-22-06
The editor is now available for download !!
It's freeware, like free beer.
It's in english.
It runs under every kind of Windows.
It doesn't need to be installed.
It puts only 1 entry into the registry (HKEY_CURRENT_USER\Software\meybohm\proton\)
I have added syntax highlighting for Dom3 mod (.dm) and for .map files, full range of commands is supported!!
WARNING: This is not longer true for Dominions versions 3.16+ ! Instead of fiddling around with the poorly documented Proton features, I might to a syntax colouring file for Notepad++ if I find the time and need ...