JeonLab @ instructables.com writes:
For relatively small (less number of pins than ATmega328) projects, ATtiny series, ATtiny45 or Attiny85 are good choice in terms of its physical size (8-DIP or 8-SOIC) and low power consumption. There are many ways to program it. One of the popular device is USBtinyISP and DASA. Both of them work very well with WinAVR (AVRdude).
ATtiny programmer using Arduino ISP - [Link]