mapmote is a powertool for OpenStreetMap editing with JOSM. It's a Chrome extension (and now a bookmarklet!) that lets you open a JOSM session from a variety of websites other than OpenStreetMap itself.
The idea came from AJ Ashton, the chief cartographer at MapBox. Using maps, while we design interfaces, debug code, and do cartography, often reveals flaws in the map data. OpenStreetMap.org, of course, has a menu that shows editing options, and the pros prefer JOSM, a powerful desktop editor.
How it does this is kind of crazy. It sniffs for all image elements
in the page, optionally detecting the map client, and then sniffs for
tile coordinates like
1/2/2.png, and then collects, projects, and
unions them into a bounding box. Once it has a bounding box, it, like
osm.org, inserts an iframe onto the page which hits a URL that JOSM
sets up for its 'remote control' functionality and passes the bounding
box to the editor.
Update it's now also available as a simple bookmarklet! Just drag the link below to your bookmarks bar and then click it when you're on a map-containing webpage.
If you want mapmote as a Chrome Extension... well, Google is being silly about the Chrome Web Store, so it's not available there. Instead, I've posted mapmote.crx in the downloads of the repository and will reproduce the hard-to-find directions here: