So I was delighted to find GeoCommons, a service to help people build maps. Unlike PowerPoint it guides people to produce good design with its wizards and templates, see the screenshot of its icon panel:
Screenshot of GeoCommons Icon Chooser Panel
Good for colors, icons and backgrounds: As you can see, you have to have a halo with your icon, a feature which I thoroughly approve of and about which I've blogged previously. And it's not just icons, when choosing fills for thematic maps you are presented with sensible color scales like the ones from ColorBrewer*. I also like the fact you can choose a blank background for your map, helpful if it is very full of symbols that are making the view cluttered.
KML Polygons?: Unfortunately it seems not to be able to cope with uploading KML Polygons which is a shame, I've emailed them to ask if I'm right about this or if I've just come across a bug but no reply of yet.
In other areas it also scores highly but this has been well documented by Stefan so I'm just keeping to design aspects in this post.
*In fact the same people that brought you ColorBrewer were also involved in designing GeoCommons.