Laszlo Hanyecz made the first documented purchase with bitcoin when he bought two Domino's pizzas from jercos for 10,000 BTC.
laszlo's Pizzajercos ordering the pizza and receiving the coins. The bitcoins were quoted at $41 at the time of the offer.
Bitcoin Pizza Index
The Pizza Index is the value of the bitcoins spent on the pizzas, were they to be sold rather than spent on pizza. It started at $41 when the transaction actually occurred, and rose significantly since then, topping at $12.4 million in november 2013.
Bitcoin Pizza Day
To commemorate the transaction, May 22 is dubbed Bitcoin Pizza Day. Pizza providers worldwide offer discounts to bitcoin users.