http://bookblog.net/gender/genie.php
This tool examines writing you input and tells you if it thinks it was written by a man or a woman. It does this based on what words are used most often where there is a difference between the sexes. On the results page it shows you which words were most typically male, and which are more likely to be from a female.
Pretty fun, maybe good practice if you want to sit there and write stuff trying to fool it...
Steph