I am using eclipse c/c++ when i create a c project then it does not shows winavr gcc in the toolchain list but i have installed WinAVR-20100110 in c drive and my eclipse is also in the same directory. it shows cygwin,solarize,linux,macosx,mingw gcc
Eclipse does not look for AVR toolchain by default, even if it is in path (you did add it there?). You need to create an cross GCC project, then tell it the prefix of your toolchain (avr- i guess). When you select "New C project" select Cross GCC in Toolchains listbox, then in next step enter the prefix, set path to toolchain (if not in path), etc. For this you need to install "GCC Cross Compiler Support". You do this from Help -> Install new software -> Mobile and Device development. You will probably also want at least GDB hardware debugging.
You can also try special eclipse plug-in for AVR.