The ESP-01 is a great wifi / IoT / Arduino "chewing gum" piece of technology, but programming it is a bit of a technical issue. Fix that with this inexpensive programmer module.
Programming an ESP0-01 (or any other ESP8266 variant) can be a bit of a button-toggling dance even after you get it wired up correctly. This handy little module makes it so much easier, by making completely buttonless and comes with a usb connector as well! Plug in your ESP-01 and use the standard ESP toolchain to do the programming. Just flip the switch to "prog" and start the programming procedure.
You'll definitely want one of these if you've ever had to breadboard a quicky-programmer adapter for these more than once!