Based on Building an Arduino on a Breadboard, a community tutorial on Arduino’s official site.

The minimalist materials list:

  • 7805 Voltage regulator
  • 2x 220 Ohm resistors
  • 1x 10k Ohm resistor
  • 2x 10 uF capacitors
  • 16 MHz clock crystal
  • 2x 22 pF capacitors

Removed items (common in stock items):

  • Breadboard
  • 22 AWG wire
  • 2x LEDs
  • (optional) small momentary normally open (“off”) button, i.e. Omron type B3F

USB to Serial Communication Board:

  • FT232RL USB to Serial Breakout Board, SKU BOB-0071 OR
  • Arduino Serial USB Board, SKU DEV-08165