Collaborative Mapping Software?

[Mortuus]

Hey folks,

I'm GMing a West Marches-style D&D game (or rather, will be shortly), and since I'm running this over the internet for a group pretty well spread geographically, I'm looking for some software I could use for the players to collaboratively update their map of the game world. My current solution is to just give them a blank page on Roll20 (which I'm using to run the game) and let them go nuts with the drawing tools, but a better option would be appreciated if any come to mind.

Thanks,

Morty

[Mipui]

My app, Mipui, supports collaborative editing. All the editors connected to the same map (=same URL) are able to edit it concurrently, with updates being propagated in seconds.

However... it's mostly intended for dungeon maps, and it's symbolic (very simple graphics, no fancy images), and it's grid-based. So it might work well for the occasional dungeon / battlemap, but it's a pretty poor solution for overland maps.