WG7 Castle Greyhawk is the one Greyhawk fans have nightmares about. (AD&D TSR, 1988)
WGR1 Greyhawk Ruins (AD&D 2E, TSR, 1990) is a lot more serious. Not great, IMO, but has its moments.
Expedition to the Ruins of Greyhawk (D&D 3E, Wizards, 2007) builds on the basis of Greyhawk Ruins, using...