Read Atmel's blurb here.

Mega8/Mega8L

We have "standardized" on the Mega8L.  Why - because it 's small and has masses of features.  The Mega series of AVR's come in two flavours: the regular or low voltage spec.  The Meg8L is the Low voltage (2.7V) version of the Mega 8 that is tested to 8MHz.  The Mega 8  is the 5V version that is tested to 16MHz. Is there really any difference between the chips? 

The Mega8's have a calibrated internal RC oscillator that is good from 1-8MHz.  I f you need a more accurate clock or faster speeds you'll need an external crystal. 

So - what do you need? It's so little it's amazing. 

1. A Mega8L chip.
2. A resistor connected between pin 1 and 7 to pull the reset pin high (something between 20k & 100K, I used 56k because that's what I had)
3. A board and 28 pin x 0.3" dip socket. (e.g. I -AM board)
4. Headers to connect the programming cable

I have assembled this SAM-I-AM board (Intelligent Add-on-Module for the SAMBot) with everything necessary to start programming. You can see the pull-up resistor on the Reset line.  I have a common ground wire but you need to be careful not to create ground loops so make sure you have only one. There's no voltage regulator because I'm going to run it from 4AAA cells (or 2 lithium cells)

I'm using PORTD for outputs to my motor controller and PORTC as inputs from the edge detectors and object sensors.  I'm trying to avoid using any of the multifunction pins.

It's that simple

Cheap like borscht!

 If you can't get an I-AM board, Radio Shack have a similar small prototyping board for under $5.00