A high percentage of Greyhawk campaigns will take place in and around the namesake Greyhawk City, and no one can run such a setting without a map! Here are a couple links to versions of that city which you will find useful if you haven't seen them already by now:
Recently, but before I started this blog, Greyhawk Grognard posted a fan-made map of the city based on the map from Gygax's novel City of Hawks. The download is big but the old-school feel of it is worth the effort. Thanks go out to Joe Bloch for sharing and Alex Camacho for his work of art.
Many of you will also be familiar with the revised map from the "blue box" City of Greyhawk done by Maldin back in 3rd edition, for the Living Greyhawk Journal. While out of print now, Maldin's site also includes his revisions for the city's sewers that never saw print by the RPGA. These maps can still be found on his site, in addition to pop-up labels for locations.