Gender is an R package which takes names and associated dates or ranges of dates and predicts the gender of the name. The gender package is now on CRAN for the first time; you can also see the package README at GitHub. This is the package description:
Encodes gender based on names and dates of birth, using either the Social Security Administration’s data set of first names by year of birth or Census Bureau data from 1789 to 1940, both from the United States of America. By using these data sets instead of lists of male and female names, this package is able to more accurately guess the gender of a name, and it is able to report the probability that a name was male or female.