The ATtiny2313 seems to be the “coming of age” chip in the AVR scene. It is very powerful and pretty small. There are many projects that use this chip
Breakout board for ATtiny13a, ATtiny25, ATtiny45, or ATtiny85. It has a 6-pin ISP header, all the data pins are lined-up for easy usage, reset button, and JST power.
The Brain Machine (Sound & Light Machine)
Trippy brain hack.