REVISED.
Development boards save time otherwise spent wiring up AVRs on breadboards and then pulling them up to make space and then re-wiring them up again later on. This board already has best practice support components around the AVR such as the noise and static protection on RESET and the bypass capacitor for the AVR power supply, which greatly improves the accuracy of the ADC.
There is also a Colpitts oscillator on-board so that the external clock may be driven by inserting a crystal and closing the XCLKEN jumper ( and then programming the relevant fuses in the AVR).
Revision 2 has tie points for GND, VCC and RESET, can now optionally be powered by the 10-pin ISP cable and also has a "Power OK" LED.
The archive contains a gschem schematic and a single-sided pcb layout.