Using Arduino microcontrollers without board
I have a post about a breadboard Arduino - in that I demonstrate the minimal amount of parts you need to use the controller (which is not much).

Example of wiring it up:



If you want to use an external crystal or resonator you can add that to the board like this:



8 MHz crystal shown, but you could use 16 MHz. Or change the fuses and use the internal oscillator.



Schematic showing how you could (if you wanted) add an ICSP header and an FTDI header: