A new version of Quantum GIS, the free, open-source and user-friendly GIS, has been released today.
See the official blog for all the details, but the most exciting addition for me is the OpenStreetMap integration. Now, you can download data directly from the OSM servers, into the application. OSM-like stylings are applied to the data to make it look a bit more like a map, and you can easily can view all the tags and relations on each object. You can also edit the data directly in QGIS, as if it was normal GIS data, and then save it straight back to the server. This could potentially make it a good alternative to the Potlatch and JOSM editors that are currently used for the bulk of additions to OpenStreetMap. The integration isn’t perfect – I got a server-side bounding box error on my first attempt out downloading data which should have been caught locally – but it’s pretty impressive nonetheless.
With QGIS’s excellent python integration, it should be possible to write other plugins, to, for example, create well-shaped building outlines with perfect right angles. I think you can do this in JOSM too, but I’ve always found JOSM a rather unfriendly application to use.