Been back to building a set of maps for a new project. And two of my recommended tools are:
Google MyMaps (powerful but with an annoying limit of 10 layers which means me needing to split maps unnecessarily)
and the excellent tool from MySociety (open sourced society!) called MapIT. A great source of UK map data – especially KML versions of authority boundaries which was what I was after!
If you’re mapping, take a look at these tools.