Chinese Gender Predictor
How accurate is it? It is believed to be approximately 75% accurate (3 out 4 chance it will be correct).
Note: A common idea is that the Chinese Gender Calendar should be based on lunar cycles, as per the agricultural calendar (yin-yang-li). But since the Chinese Gender Calendar has its roots in astrology, which is based on the sun's movement around the zodiac, perhaps it makes more sense to use solar calendar dates. In fact, the research on this site shows that the highest accuracy is achieved when western dates (in accordance with the Gregorian calendar) are applied. In other words you don't need to convert birth dates and conception dates into other calendar systems.