For completion, I'm including the product line information here for interested parties:
8050 CZ1 Castle Zagyg: Yggsburgh - by Gary Gygax (2005)
8060 CZA1 Castle Zagyg: Dark Chateau - by Rob Kuntz (2005)
8059 CZ9 Castle Zagyg: The East Mark Gazetteer - by Gary Gygax & Jeff Talanian (2007)
8051 CZ2 Castle Zagyg: The Upper Works - by Gary Gygax & Jeff Talanian (2008)
8061 CZ10 Free Town of Yggsburgh: Town Halls - by Jeff Talanian (2007)
8062 CZ11 Free Town of Yggsburgh: Moat Gate - by Don Macvittie (2007)
8063 CZ12 Free Town of Yggsburgh: The Store House District - by Jeff Talanian (2008)
8064 CZ13 Free Town of Yggsburgh: The East Corner - by Joe Damiani (2008--PDF only)
PDF Excerpts from CZ1
Castle Zagyg: Yggsburgh Preview - table of contents, pp. 4-7 (free)
CZ PDF1 Castle Zagyg: Class Options & Skills - multi-classing & secondary skills rules for C&C (free)
CZ PDF1 Castle Zagyg: Class Options & Skills - Talanian edit (free)
CZ PDF2 Castle Zagyg: Player’s Maps - unkeyed city & environs maps drawn by Darlene
CZ PDF3 Castle Zagyg: The Outs Inn - pp. 92-101
PDF Excerpt from CZA1
Castle Zagyg: Dark Chateau Preview - basically just p. 3 (free)
PDF Exerpt from CZ9
Free Town of Yggsburgh: Town Map - city map keyed by district, drawn by Peter Bradley
To round out what would be considered the final piece of the existing info on Castle Zygag, we must turn to Jeffrey Talanian, whom co-wrote with Gary the Upper Works. In Issues 9-12 of The Crusader Journal - a magazine by Troll Lord Games there was additional information written. I'm including Mr. Talanian's reply herein:
I wrote the first one as an historical perspective of the project. Gary edited it for me. Two weeks later, Gary passed away, so I wrote the next piece all about the man I knew, my friend Gary. The next two issues were pure adventuring material, expansions to the whole and worthy of inclusion in any Castle Zagyg game, IMO.
Finally, Jeff made available a work called: Castles & Crusades Castle Zagyg The Workhouse of Yggsburgh Town - a 3 page write-up on one small encounter within Yggsburgh. It is here that Jeff shows his genius, and I for one wish he would have continued on with the series after Gary's untimely passing.
Here is all the items recommended in order to run WG13 Castle of the Mad Archmage!
S3 Expedition to the Barrier Peaks
EX2 The Land Beyond the Magic Mirror
WG6 Isle of the Ape
Garden of the Plantmaster
MC10 Ravenloft Monstrous Compendium
Hacklopedia of Beasts
The Living Room
Adventures in Oz
To be continued when the party begins to explore the Mouths of Madness...