Sometimes, you need only few input and output from microcontroller for your project. If you use Arduino, it would be costly and need more space. For small project like infrared pc remote control, an ATtiny85 microcontroller is good solution. It has 8 Kb flash memory, 6 input/output pins, low power supply at 1.8-5.5V, small 8-pin packaging and costs only 2-3$.
To program ATtiny85, you can use your Arduino board as ISP programmer. For easy and fast ATtiny85 programming process, you can try ATtinyShield made by Koursaros. This shield is built based on tutorial by MIT’s High-Low Tech research group. The shield’s hardware consists of few socket, passive component, jumper and small PCB.