How to read passive RFID cards using Android?

Hi all,

Can anyone please let me know if it is possible to read passive RFID cards using Android phone?

Frequency range of passive RFID cards that i m interested in is 13.56MHz

I have Droid incredible but i have not seen any serial port where in I can insert RFID reader..

Any information about how to read passive or active rfid cards using android is appreciated.

thanks
siddhesh