You will need the following:
- Arduino of some kind. I have been building my own on stripboard, but recently bought some "Evil Mad Scientist" ATmegaxx8 Target Boards
to use in future projects. If you build your own you should add a "protection diode" on the + side of the input voltage. An IN4001 or similar will work.
- Parallax RFID Reader Module
- HD44780 compatible LCD display. I find a black on yellow works best in daylight vs a blue on white. I get mine from DipMicro
- Small 10K trim-pot for the display contrast.
- 5v Boost Regulator
For this project I wanted 2x AA to power the device as most geocachers carry them. However with the code I use they drain in about 1 1/2 hours, so a 4x AA may be a better option
- hook up wire. I use wire from cat5 stranded patch cable.
- case of some sort. I used a clear blue case found at most electronics stores.