From what I can tell by searching online, Andrew Main's Stardate FAQ is fairly popular, and I really like it myself.
I can't, however, seem to find much in the way of programs/scripts that take advantage of this FAQ (or the C file located on the same site). The closest I could find is this, which only displays the current date.
Is there anything out there which uses the information from the FAQ? A downloadable program, a JavaScript applet, a PHP script? I love knowing today's stardate, but I also want to be able to convert any other theoretical date to the relevant stardate, and any stardate to a real-world date.