Wow what a great freebie this is! The Pinkwear are currently offering a free trial where you can 3 pairs of premium panties delivered straight to your door. Just pick your size and which style you want (Briefs, Thongs or Mixed) and fill out your details on their site.
This is a subscription service but you are free to cancel at any time. It's well worth carrying on after the first month though as you'll receive different designs each month.