You will need an SD Card and some way of connecting it to an Arduino. The easiest way is get an SD/MMC Card Breakout Board from various electronics hobbyist suppliers. I used one from Sparkfun.
|SD Card & Breakout*|
|3 × 3.3K ohm Resistors|
|3 × 1.8K ohm Resistors|
|*image courtesy of Sparkfun|
The resistors are to create a voltage divider and to drop the 5v logic levels down to 3.3v. ...