The European Centre for Medium-Range Weather Forecasts (ECMWF) makes 10-day weather forecasts for most European weather offices. They started switching most of the desktop sytems to Linux a year ago, and have chronicled the conversion in one of their newsletters.
The article is within the Fall 2001 edition of the Centre's newsletter and provides quite a bit of technical detail on the Centre's switch to Linux workstations.
[Editor's Note: This is a PDF article. The Linux story runs on pages 12-15 of the document.]