I just know three face recognition sites that attempt to figure out both gender and age: skybiometry, pictriev and now thanks to your post, how-old.
Of those three, Pictriev is totally off IMO, both in gender and age. I get readings all over the place. Skybiometry is by far the most accurate. Very realistic in the gender guessing, but way off in the age part. How-old is a bit accurate too, apparently. But I prefer skybiometry because it even attempts to tell you how much female or male you look, in percentage, but unlike pictriev, it only mentions one gender and its percentage, not the two of them.
Now, what I would really like to find is a face recognition site that can tell you what kind of face you have (oval, heart-shaped, square, round, oblong, pear, triangle, or combinations), because knowing exactly what kind of face one has, can help determine the most feminine hair style for one's particular face.
