FT232RL USB to Dupont Cable 4p
Phoenix Technology's own PICAXE programming lead. This cable brings a 4th wire down from the USB port with 5v on it, allowing you power your project from the computer.
The 5v power means you can power your project, or power and recharge the PICNano or any other applicable rechargeable battery. This means no more throwing out and purchasing of batteries! Or, if you're a teacher, no more students losing them!