After you’ve installed the necessary drivers, the next step is to download and install a compiler. WinAVR, located at http://winavr.sourceforge.net/, is an open source suite of software development tools for the Atmel AVR series of microcontrollers. It includes the GNU GCC compiler for C and C++. Follow the installation instructions they provide.
WinAVR alone will give you all the tools you need to start programming your Orangutan or 3pi robot, but Atmel offers AVR Studio 4, a free integrated development environment that works with the GCC C/C++ compiler. AVR Studio 4 includes a simulator and other useful tools, and supports the AVR ISP protocol used by the Orangutan USB programmer. You can download AVR Studio 4 from Atmel’s website. Follow Atmel’s installation instructions. Note that newer versions of AVR Studio 4 might not work with older versions of WinAVR, so we recommend you upgrade to the newest version WinAVR every time you get a new version of AVR Studio 4.
The Orangutan USB Programmer is not compatible with the newer AVR Studio 5 or Atmel Studio, but the newer Pololu USB AVR Programmer is.