Mikel Maron is a fan of dot grid maps:

Dot grids are a clear, informative, multidimensional and flexible cartographic technique. They effectively leverage patterns of human perception to present information dense but readily comprehensible maps. Compared to choropleth maps, dots retain the base map context, and invite us to fill in the gaps. They emphasize the limits of data sampling. Dot grids can be joined together across different boundaries flexibly. The density of a dot grid can be varied depending on the scale. And that visual regularity … it just looks so cool.

He offers some examples of dot grid maps from his work at Earth Genome (see e.g above), and elsewhere, and gives some history of the format.