Rfid-1RFID Toys looks excellent! And it’s written by MAKE pal Amal Graafstra“The book contains step by step guides to building various RFID based projects, and stresses the concepts involved as well as the steps themselves. RFID technologies covered include passive, low frequency 125KHz tags and readers, passive high frequency 13.56MHz, up to active, UHF 900Mhz tags and readers.” Thanks Matt! Link.