The RC522 is a 13.56MHz RFID module that is based on the MFRC522 controller from NXP semiconductors. The module can supports I2C, SPI and UART and normally is shipped with a RFID card and key fob. It is commonly used in attendance systems and other person/object identification applications.
Each Model of HC Bluetooth is very popular for using with any Microcontroller such as Arduino or STM. Bluetooth is easy for you to control wirelessly any device in short rang via your Phone or Computer. Bluetooth model of HC have communication protocol UART.
The OLED displays are one of the most attractive displays available for a microcontroller. It has a good view angle and pixel density which makes it reliable for displaying small level graphics. Interfacing this IC with MCU can either be done using IIC or using SPI hence helps to save some pins as well.
So if you are looking for a slim, attractive and efficient display module to make your project look cool with graphics then this module might be the right choice for you.
The Arduino Nano is a small, complete, and breadboard-friendly board based on the ATmega328 (Arduino Nano 3.x). It has more or less the same functionality of the Arduino Duemilanove, but in a different package. It lacks only a DC power jack, and works with a Mini-B USB cable instead of a standard one.