Moon festival will be on Thursday September 19th. It's a quasi important festival for the Chinese since it celebrates the middle of autumn (8th month and 15th day).
So along with feast foods you get to eat the little mooncakes. Traditionally the filling of the mooncakes is made out of lotus paste with duck egg yolks to symbolize the moon. However for the past 20 years people were starting to change the filling to make it more interesting. Now you can get fillings made out of red bean paste, date paste, ube paste, coconut or even durian!!!
Stores have been selling them of the past couple of weeks. You can even get some crappy ones at costco. In the triangle area you can simply buy them at local Chinese supermarts such as Grand Asia, A&C and Li Ming's. I recommend the brand "Wing Wah" as they make some of the best mooncakes money can buy. I'm a purist so I go for the plain lotus paste mooncake.
Now you can even buy mooncake molds online but I prefer store bought...