This is a two channel analogue digital converter example project using I2C communication to use with the Raspberry Pi. However, it will work with other setups using avrdude and ISP programmers.
You'll need the files for usitwi / I2C communication installed - you can copy them to the same folder as the C file above. You can read on how to setup I2C communication between a Raspberry Pi and an ATtiny here on my blog. This includes tips on avr programming, too.