The map provided in the Extras section for the game has only just over half of all areas marked. Use this one at Gamebanshee.com. This page even provides a list of coordinates for all locations. I don't think it has areas from official modules or areas restored from cut/incomplete content that are added back in the game via fan patches.

That's a great map, but would probably be considered a spoiler for someone who hasn't played the game before. Many of those locations are supposed to be secret until the player learns where they are.

They can do what I do, and look up a "recommended sequence of play" or something. I mean, there are certain places you want to get to early on in the game. Like the Old Blind Master's House, where you can get the best thrown weapon in the game, the Aerial Decapitator (ripped right out of Master of the Flying Guillotine, replete with sounds ripped from the same movie). It's not marked on the map and not part of any quest, but the coordinates are on the page I linked to. And information about individual areas can be found on the right hand side of the screen, after clicking "Walkthrough" on the left hand side. Game Banshee divides the areas into Major, Minor, Optional (mostly Easter egg stuff), and "Other Quest Areas".