AVR-Eclipse is a plugin for the Eclipse IDE which adds toolchain support, through CDT, for the gcc compiler for the Atmel AVR series of microcontrollers, and adds a toolbar button to allow quick upload of produced code to a target device.
Takes a bit of learning, and on my old computer, a bit slow...but marvellous once you get the hang of it.
Plugin seemed not to work with the avr make.exe under Windows 8.1 (Windows 8 works). Tested with Juno + Kepler + Kepler-32Bit. An other make.exe (from Sourcery_CodeBench_Lite_for_ARM_EABI) fixed it. Armin