There are a number of RFID readers out there. I used an RFID ID-12 (SEN-08419) chip with the breakout board(SEN-08423) from Sparkfun.
You basically hook it up to the serial pin. When a card is swiped it sends the card ID over the serial line.
Here is a small test program to give you an idea of how easy it is. I X'ed out the card id's (also from sparkfun).
char val = 0; // value read for serial port
char peopleCardID[][20] = {
"XXXXXXXXXXX","XXXXXXXXXXX","XXXXXXXXXXX","XXXXXXXXXXXX","XXXXXXXXXXXX"};
char people[][20] = {
"Ted", "Frank","Johnny","Franny","Bobby"};
void setup() {
Serial.begin(9600);
}
void loop () {
int i;
char card[20] = "";
if(Serial.available() > 0) {
boolean bFound = false;
i=0;
while(Serial.available() > 0){
val = Serial.read(); // read from the serial port
if ((val >= 'A' && val <='Z') || (val >='0' && val <='9')){
card[i++] = val;
delay(10);
}
}
card[i] = 0;
for (i=0;i<5;i++){
if (!strcmp(peopleCardID[i],card)){
bFound = true;
Serial.print("Hello there ");
Serial.print(people[i]);
Serial.println("!! ");
}
}
if (!bFound){
Serial.println("Unknown Key!!!");
}
}
}
Also here is a link to a project someone did with it with more details. It has wiring diagrams and code as well. Mark Fickett | Art Stuff | RFID Meter
Adafruit also has an RFID shield that you can look at. No wiring needed and she has a library and sample code to use. Here is the link to the basic sample code Adafruit_NFCShield_I2C/readMifare.pde at master · adafruit/Adafruit_NFCShield_I2C · GitHub