danbri\s foaf stories point us in the direction of some great-looking screenshots of an upcoming open source client-side map editor, MozMapEditor. (It uses XULRunner, so it’s aimed at Firefox et. al.)
ETA is the beginning of September, as per the comment thread. Did I mention it looks great? The mozdev site explains,
Mozmapeditor is based on a new implementation in Mozilla, the Scalable Vector Graphics (SVG), and on an Open GIS Consortium (OGC) standard, the Geography Markup Language (GML).
Danbri hopes the results are exportable to KML, among other formats, and so do I. It shouldn’t be so hard, right?