You're a bit early, Pizza Day is on May 22. Laszlo's thread was started on May 18, 2010, but the transaction took place on May 22 (at least at this day @laszlo confirmed the transaction).

For those searching a local merchant afaik BTC Map is one of the best worldwide directories as of now, as Coinmap has closed. There are also local directories (for example Coinpages for the German-speaking world). There are also lists at the websites of payment processors like Bitpay, CoinPayments etc.. As a last resort there is Bitrefill, Coincards etc. for gift cards -- however, it's likely that the merchant doesn't even know that they are paid in Bitcoin in these cases.