TileMill is an application made by MapBox (link) which allows for users to create and edit maps using an interface similar to such GIS programs as Quantum GIS or ArcGIS, but with a decidedly design-oriented flair. Instead of providing the graphic user interface that utilizes tools, buttons and forms, TileMill utilizes a style of CSS called cartoCSS. This allows users to develop their maps with a much more flexibility and power. TileMill is free to download and can be used to create a variety of maps based on data and can export images in PNG and SVG format, as well as MBTile files. The latter can be opened to show the same interactive image as that showing up in the TileMill preview window, and as well, these can be served to make online interactive map applications (using tilestream or MapBox servers).