WinAVR is a great tool to do development for Atmel AVR micro-controllers on Microsoft Windows platform. It consists of all the necessary C/C++ compiler, linkers and other GCC tools that you need to write, build and program those micro-controllers.
WinAVR: http://winavr.sourceforge.net

Here we have put together very short guide how to setup and use WinAVR for programming the Attiny85 micro-controller and the Tinusaur Board in particular.
The guide was tested mostly under Microsoft Windows 8.1 operating system.
The example source code was tested on ATtiny85 micro-controller installed on a Tinusaur project boards and programmed using USBasp ISP programmer.
Please go to WinAVR – Setup Guide page to read the entire document.
A Mac OS X guide too?
Hi JD,
I don’t own a Mac so I can’t write a guide for it.
Next week I’ll be writing a guide how to program the Tinusaur with the Arduino IDE so that may work well on Mac OS too.