The Palmist - a site with a lot of good information on ModMaker.
Home of the OxBow module.
Guyver AC Add-ons - a site with a lot of good information on ModMaker.
Home of the Fell Keep and Gladiator modules.
Rob's Aldon's Crossing stuff - Home of the free unix-based module editor (a unix ModMaker). There is also a ton of Module making information here as well.