I have 2 pre-3E WotC products sitting on my gaming table at this very moment! They are two 2nd edition guides to Greyhawk printed around 1999/2000: "The Player's Guide to Greyhawk" and "Greyhawk: The Adventure Begins". I am using them both to help provide background for my Age of Worms campaign.
I use the "Player's Guide" for its comprehensive list of deities (with their alignments and portfolios) and for the well-done geopolitical map of the Flanaess (which is *far* superior to the one that came with the Greyhawk Gazetteer).
I use the "Adventure Begins" book mostly for its breakdown of the Greyhawk calendar and lunar cycles as well as its random weather tables.
I use the "Player's Guide" for its comprehensive list of deities (with their alignments and portfolios) and for the well-done geopolitical map of the Flanaess (which is *far* superior to the one that came with the Greyhawk Gazetteer).
I use the "Adventure Begins" book mostly for its breakdown of the Greyhawk calendar and lunar cycles as well as its random weather tables.