Glenn Grant has blogged recently about going down the USB Reverse Engineering rabbit hole [devalias.net]. He does a deep dive into the software and hardware used to reverse engineer, do protocol analysis, do hardware hacking, and do what whatever else would be involved in implementing custom drivers for arbitrary hardware. USB is a ubquitous, industry standard for cables, connectors, and their supporting protocols with a surprising amount of computing power running internally on chips inside the USB devices themselves.