SockCalc started life as an web tool I wrote in 1996 to learn cgi programming.
The online version is still available at http://www.arachne.com/sockCalc/socks.html
The Sock Calculator was mentioned in Stitch n Bitch, Craftlit, and it has a Ravelry design page.
I thought it would make a perfect iPhone / iPod Touch application - small, convenient, and always in your pocket when you want to whip out a pair of socks.