PinFilly had designed cutie mark pins a while back and put them up for pre-order. They had been ordered along with a lot of extra pins to sell regularly to those who missed the pre-order. According to PinFilly herself, they will be arriving in bulk to her business/residence next week and those who pre-ordered should start seeing them in about 2 weeks!
And for those who want in on the pins, look no further: http://ponyorders.ecrater.com/. They are priced between $2-$3 each.