The Mid-Autumn Festival, also known as 中秋節 , is held on the 15th day of the 8th month in lunar calendar (which is around the period of late September/early October). I cannot quite remember the story behind this festival but I know it's about eating mooncakes and pomelo, carrying paper lanterns and admiring the moon (supposingly at its fullest and roundest time of the year).
From my vague memory, the story behind Mid-Autumn Festival is about 嫦娥 and her husband, 后羿 (a Chinese archer) and the Ten Suns blazing the Earth. 后羿 shot down 9 Suns but spared 1 to be the Sun. 嫦娥 became the Moon Fairy (I can't remember how and why) and some people set up altar in the opening air facing the moon to worship her . There are at least 6 versions to this story so check it out here if you want to find out more. As far as I'm concern, I'm just happy making and eating my mooncakes :P
Here's wishing all bloggers/visitors: 中秋節快乐
Just a note, next year's Mid-Autumn Festival falls on 22 September 2010.