This board will let you add WiFi functionality to your Raspberry Pi Zero without having to sacrifice the only available high speed USB port. The board is based on ESP8266 Wifi module.
WiFi on a Raspberry Pi using the HAT connector and an ESP8266. The goal of this project is to add WiFi to the Raspberry Pi Zero while keeping the USB port free for devices or OTG connection to another host.
Raspberry Pi Wifi module without USB – [Link]