There's no simple USB hack.
There is the x360key (xk3y), and Wasabi360 which are the easiest hacks for 360 right now as all you have to do is connect the device to your 360 drive and motherboard (no soldering or flashing the drive needed) and it will emulate disks from ISOs on an external hard drive (also connected to the device).
These devices are around $100 USD