an Arduino Ethernet board and a USB-to-serial programming adapter such as the FTDI Friend or
TTL-232 Cable.
-or-
an Arduino Uno board and Ethernet Shield.
Directions are provided for both. In either case, you will also need:
Cables for USB programming and Ethernet.
Not included with the kit, the following tools are needed:
Soldering iron and solder.
Small Phillips screwdriver.
Optional: tape, pliers.
Not shown: wire cutters and strippers, lighter or heat gun for heat-shrink.