20pcs CP2102 USB to TTL Serial Adapter Module USB to UART Converter Debugger Programmer for Pro Mini OPEN-SMART for Arduino - products that work with official for Arduino boards
FT232 USB UART Board (Type A) USB TO UART solution with USB Type A connector
USB-UART converter for WIFI ESP8266 ARDUINO module
SparkFun USB UART Breakout (CY7C65213) Hookup Guide - SparkFun Learn
PL2303 USB to Serial UART TTL Adapter Board (type A) V2 for Arduino Windows 7 8 | eBay
USB to TTL UART Isolated for Arduino pro mini – DuPPa
USB-UART for Arduino ESP - like FTDI, CP2102 etc. from ArduinoShop on Tindie
USB UART/I2C Debugger for Raspberry Pi, Arduino – Oz Robotics
How to Use Arduino as USB to Serial Converter | Microcontroller Tutorials
FT232R USB UART Arduino Nano : 5 Steps - Instructables
Arduino USB 2 Serial Micro | Arduino Documentation | Arduino Documentation
WITMOTION USB-UART Converter 3-in-1 Multifunctional(USB to TTL/ USB to RS232/ USB to RS485) 3.3-5V Serial Adapter, with CH340 chip Compatible with Windows 7,8,Linux,Arduino for Development Projects