Cam from Threadless.com sent me this link to get 20% off on any purchase when you spend $25 or more. Discount shall be applie to your account automatically. Not too sure about the expiry date but Cam said that they have this running as their free shipping offer just ended today.
4 x Tees
Order summary
Item(s) cost: $69.00
Shipping cost: $15.00
Tax: $0.00
Subtotal: $84.00
-$13.80 ( International Offer)
Total cost: $70.20
Cheers!