Not much is needed for this lesson, just a USB cable and an Arduino or compatible.
Assembled Arduino board, preferrably an Uno or Duemilanove (or whatever the latest version is)
Arduino compatibles will work but there's a lot of issues with ultra low cost 'Arduino compatibles' (e.g. eBay, Amazon, etc) where they have shoddy substitutions that can bite you later. It's good to have at least one known-genuine Arduino UNO!
You can also use an Adafruit Metro which is a drop-in replacement for the UNO, some components like the LEDs are in different locations.
USB Cable, any length. The cable should match your Arduino's USB connector. Official Arduino UNOs use USB "Printer Cable", a blocky cable. Some compatibles use USB Mini-B or Micro-B.