RFIDuino is an Arduino shield for reading and writing 13.56 MHz RFID

tags. It consists of a 65x65mm circuit board, which plugs upside-down onto a

standard Arduino (NG, Diecimila, Duemilanove, or BlueTooth).
The board has a build-in
antenna and contains all the circuitry to read and write 13.56 MHz ISO-14443A (Mifare) RFID tags. It is connected to the Arduino by I2C, using the Wire library.

I build a prototype during Picnic ’08, documented here.

The production version will be available
in my web shop from early April.