Avr-Eclipse Plugin for Eclipse

This thing is great (see the screenshot). You get all the fancy-shmancy auto-formatting, project handling goodness and slick GUI of eclipse, yet it will still directly burn your .hex to your AVR micros with a single click. Oh yeah, and it runs in linux :p.

You will, however, need to install the rest of your toolchain (avr-gcc) separately, and the website has a guide to do this. I just got my first blinky LED program going as seen in the image above, so I know the whole deal works. Next task is to get in-circuit-debugging working. (I think this is supposed to be supported..)

Site: http://avr-eclipse.sourceforge.net/