GitHub repository: kring/grisu.net
Primary language: C#
Description: Grisu is a fast, new (2010) algorithm for converting a floating-point number to a decimal string.  It was introduced in a paper by Florian Loitsch (http://dl.acm.org/citation.cfm?doid=1809028.1806623) and the author claims it to be as much as 4 times faster than previous techniques.  The code here is a port of the C++ code in the "double-conversion" project on Google Code (http://code.google.com/p/double-conversion/) to C#.