I have always been partial to the World of Greyhawk map.
Dungeon magazine (current issue #116) will, over the next few issues, be presenting a new large Version of the World of Greyhawk map as a series of four poster-sized maps (issues #117-120).
That aside, lots of board wargames use hex maps. One source is
Strategy & Tactics magazine, by Decision Games
(see here).
Each issue has an historical game, and many of these have hex maps.