RFID systems come in a myriad of forms, each catering to a specific need. However, a systematic classification to reduce the confusion of potential adopters, researchers and enthusiasts is still lacking. This article proposes and evaluates a taxonomy of various RFID systems currently available. The taxonomy can be used for gaining an understanding of this technology, the factors for implementation of a successful RFID system, its strengths and weaknesses as well as scalability options. Both novice as well as experienced RFID researchers will benefit from this classification.