I am working with the ATMEL ATMEGA8 microcontroller

To program it I use the AVR ISP Serial Programmer Kit. I have used this programmer both with a built in serial port and a USB-serial adapter. Both work fine.

I do my development on various laptops, all of which have unbuntu linux installed. I have installed various avr related packages such as avr-gcc and avrdude. You can find them by searching in the Synaptic package manager.

I have written a number of applications. The source code is available online. Note that only a few of the repositories at that location are atmel apps.

A good example is my robot arm controller. I haven't written many circuit diagrams however I do maintain a hardware wiring document which tells you what connects to what.

The microcontroler is documented with a very comprehensve PDF document. Everything you need to know really is in there but it does take a bit of hunting around.