Step 2: Put three nail polish colors in the shopping cart/bag.
Step 3: Type "TW5000" as a coupon/promo code.
Step 4: Pay $7 in shipping.
Step 5: ???
Step 6: Profit... with three free nail polishes.
Just make sure to only put the $6 polishes in your cart, as the promo code only gives you $18 off.
This offer expires at midnight PST unfortunately.
Its also been brought to my attention that you can get 5 free nail polishes for the cost of shipping from ELF by using coupon code "R0213097FD59A" at checkout.
I do not know if there is an expiry on this one.