WinAVR (tm) is a suite of executable, open source software development tools for the Atmel AVR series of RISC microprocessors hosted on the Windows platform. Includes the GNU GCC compiler for C and C++.
This is absolute crap. Instead of appending something to the PATH environment variable (Win7, 64bit) this installer overwrites it, leaving the rest of your system completely screwed. DO NOT INSTALL
*Warning* This suite can mess up your PATH variables in Windows 7, which means many of the CMD shell commands you need to use like find.exe and sort.exe will be used from the WINAVR bin folder, breaking loads of stuff. Otherwise its a good toolkit.
WinAVR destroyed my Windows PATH! >:(