FatFonts [fatfonts.org] is a novel numeric typeface for data visualization purposes. The design of FatFonts is based on Arabic numerals, but the amount of ink (i.e. dark pixels) used for each digit is proportional to its quantitative value. This font enables the reading of numerical data while still preserving an overall visual context.
The typeface was developed by Miguel Nacenta of the University of St Andrews, and Uta Hinrichs and Sheelagh Carpendale of the University of Calgary. In the online gallery several case studies are documented on how this font can be used for good used. More detailed information about these examples can be found in their academic paper (PDF), while more interactive examples can be viewed here.
The fonts themselves can be downloaded here.