With regard to Google Mapmaker I've done a before and after shot of the area around Reykjavïk. On the left is the shot of google maps as it stood a few minutes ago. Blank. On the right is mapmaker - the data here, once it is more consistent and complete should find its way over to google maps proper.
Google has opened up its mapping software for certain areas. It can be a little clunky at times (the list of edits I've made isn't exhaustive, if something is awaiting moderation it cannot be tweaked easily and so on). It's not always clear what the road classifications are supposed to be - but I'm working on the basis that if I put in a best guess, it can always be tweaked if not quite right. Nevertheless, it can be fun, as well as useful (I've been mapping Iceland, I've done a lake, Klerfarvatn, a glacier, and lots of roads concentrating around the Blue Lagoon and Grindav&iaciute;k in the south west). Some of my changes have been accepted immediately, some depend on other changes, and so are pending, and some are in moderation awaiting checking.
Maps are currently editable in a few areas, probably selected for the lack of existing map features, so if the mapping experiment fails, google can delete the mapping info and be back to where they started.
The areas editable right now are: Antigua and Barbuda, Bahamas, Barbados, Bermuda, British Virgin Islands, Cayman Islands, Cyprus, Grenada, Iceland, Jamaica, Netherlands Antilles, Pakistan, St. Kitts and Nevis, St. Lucia, St. Vincent and the Grenadines, Trinidad and Tobago, Vietnam.
Even changes which are approved take a little while to be rendered and appear on the maps - this is especially true for some large features.