Itoworld has produced a stunning animation [vimeo.com] showing edits to the OpenStreetMap project during 2008. OpenStreetMap [www.openstreetmap.org] is a wiki-style map of the world that anyone can edit. The animation shows worldwide contributions to the project over the course of 2008 and whenever a line is edited it flashes white and slowly fades out. You can see the beginnings of whole towns, states and countries and the steady refinement of existing data in more detailed areas.
OpenStreetMap's data comes mainly from users tracing over GPS tracks they have contributed, ensuring the data is free of existing copyright restrictions and can be shared under a Creative Commons license. In some countries the maps have been created entirely from scratch, while in others existing geodata has been imported either from generous donor companies (e.g. AND in the Netherlands) or from public domain sources (e.g. the TIGER-line data provided by the US census). Yahoo! also allows the use of its aerial imagery for OpenStreetMap users to trace, and other out-of-copyright aerial imagery and maps can be used too.
In the past few years the OpenStreetMap project has gone from strength to strength, documented on its comprehensive wiki, and the Itoworld animation shows that 2008 was its most impressive year yet. The usage statistics tell a compelling story about the growth in number of participants and contributed data, countless blog posts like this one, this one, and this one cheer the project on, but it's the resulting maps that speak for themselves.
OpenStreetMap showed early potential for being more than "just" a copyleft project when places such as Baghdad (map) were mapped using aerial imagery alone, long before any OpenStreetMap users ever set foot there. Now contributors all over the world are mapping their local areas too, there are frequent calls for participation to map areas in need (like Gaza) since the coverage of OpenStreetMap in many places exceeds the offerings of commercial mapping APIs.
Applying the wiki paradigm (aka crowd-sourcing) to mapping is certainly a compelling prospect, so much so that Google is doing it too with its MapMaker product. The MapMaker team is also producing progress animations and images (via O'Reilly Radar) similar to those produced by OpenStreetMap contributors to illustrate their progress. However, so long as Google owns the copyright to your MapMaker contributions, keeps the vector data to itself and has to selectively enable the tools in a particular region then the similarities to OpenStreetMap pretty much end there.