- Dave Arneson's Blackmoor D20 Hardcover Sourcebook (D&D 3.5 Edition) (2004)
- The Redwood Scar (D&D 3.5 Edition) (2006)
- The Wizard's Cabal (D&D 3.5 Edition) (2006)
- Original Blackmoor Map pdf, by Dave Arneson (2006)
- The Dungeons of Castle Blackmoor (D&D 3.5 Edition) (2006)
- Dave Arneson's Blackmoor Softcover Sourcebook (D&D 3.5 Edition) (2006)
- Player's Guide to Blackmoor (D&D 3.5 Edition) (2006)
- Temple of the Frog (D&D 3.5 Edition) (2007)
- Clock and Steam (D&D 3.5 Edition) by Rodney Thompson (2008)
- Riders of Hak (D&D 3.5 Edition) by Dave Brainard and Tad Kilgore (2008)
- City of the Gods (D&D 3.5 Edition) by Harley Stroh (2008)
- Duchy of Ten (Vapourware - Never published)
- City of Blackmoor (Vapourware - Never published)
- The First Fantasy campaign (Vapourware - Never published)
By Wizards of the Coast
- Foul Weather(2004) - for D20 Modern
- Return to the Temple of the Frog(2007)
So, in 2003 Wizards of the Coast made a settlement with both Dave Arneson and Gary Gygax making sure that neither of those men would feel that they had any claim on D&D or any of its related properties. As part of Dave Arneson's deal he also got permission to publish Blackmoor material for the 3rd Edition.
The above books were all published by Dave Arneson's company Zeitgeist Games between 2004 and 2008. When Dave Arneson passed away, WotC discontinued the license.
More on the specifics of these books later.
In addition, Wizards of the Coast published two modules that they released on their website with ties to Blackmoor. Foul Weather isn't really connected to Blackmoor, but the Temple of the Frog is a "Return to" Style adventure set in the classic Blackmoor location. It was pretty surprising when it came out that WotC would do this as ZGG were also about to release their own version of the module.
What are your thoughts on the d20 Blackmoor line?