USBasp AVR programmer with cable
A programmer like this USBasp is essential for programming Atmel AVR microcontrollers via their ISP interface. This one features overcurrent and short-circuit protection on the power lines and has on-board voltage regulators to ensure programming stability.
This programmer has a 6-pin interface and includes a connecting cable.
We've got a guide right here on our site for flashing an ATTiny84 with this programmer and the Arduino IDE.