WINAVR is windows OS tool set for AVR microcontroller based projects. This package contains an AVR-GCC C/C++ compiler. Official site of WINAVR:  http://winavr.sourceforge.net/index.html . In this site you can download everything needed to start your firrs AVR project. For this article am will using WinAVR20060421 stable distribution as it is tested and working version.

GNU Binutils - AVR target Binary Utilities (assembler, linker, etc). It contains:

    1) ld - GNU linker;
    2) as - GNU assmebler;
Also (seein  http://sources.redhat.com/binutils/ ):
    3) addr2line;
    4) ar;
    5) c++filt
    6) gprof;
    7) nlmconv;
    8) nm;
    9) objcopy;
    10) objdump;
    11) ranlib;
    12) readelf;
    13) size;
    14) strings;
    15) strip;
    16) windres.

avr-libc - C library for AVR. Normal spot to report bugs that also affect GCC and Binutils first.
avrdude - Programming software, supports lots of programmers.
GNU GCC - C Compiler
avrdude-gui - Graphical interface for avrdude
GNU Debugger (GDB) - Command line debugger
Insignt - Graphical debugger
AVaRICE - Connects the JTAG ICE to the AVR-GDB debugging software.
simulavr / simulavrxx - Simulator for the AVR
MFile - Makefile editor
Programmers Notepad - Text editor / IDE for compiler
SRecord - Tools for editing EPROM load files.