This short tutorial will show you how to setup a breadboard with an Atmel AVR microcontroller to be programmed using In System Programming (ISP). This allows you to program and re-program your chip whilst in your own circuit, without the need to be constantly removing it and placing it in a dedicated programmer.
You will need an ISP compatible programmer. These typically plug into the parallel port of your computer and have a 10 Pin IDC connector like the one shown below.
AVR In circuit programming or ISP: [Link]