When information needs to be communicated, Edward Tufte demands both truth and beauty. Very good and informative article by Fran Smith for Stanford Magazine. If you haven’t yet read any of Tufte’s books yet here’s a list for you:
The Visual Display of Quantitative Information - 1993
Envisioning Information - 1991
Visual & Statistical Thinking: Displays of Evidence for Decision Making - 1997
Beautiful Evidence - 2006
The list is not full as I added only those books that are most relevant to Web Design.