First up is a USB host shield based on the MAX3421E. This USB peripheral/host controller contains the digital logic and analog circuitry required to implement a full-speed USB peripheral or a full-/low-speed host compliant to USB specification rev 2.0.
Next up is the ArduinoISP (AVR-based in-system programmer) based on David Mellis’ project FabISP and useful to anyone needing more space on their Arduino board.
Interested in learning more? For more details about using the Arduino ISP please visit the Getting Started page. You can also learn how to program an ATtiny and read your Arduino built-in EEPROM using ArduinoISP on Scuola here.