On the list of things that might be interesting:

Did you know that you can get a linux USB driver to bind to a device it would normally ignore?
Typically, and FTDI device would have the vid:pid pair 0403:6001. But many FTDI devices end up with different sets.
For instance, I have a device with vid:pid deaf:deed. The ftdi_sio module (modprobe ftdi_sio) doens't recognize the device. If I want to serial interface for some reason, that's bad.

Try this:

root@demobox ~# modprobe ftdi_sio
root@demobox ~# dmesg -c
[95343.531550] drivers/usb/serial/usb-serial.c: USB Serial support registered for FTDI USB Serial Device
[95343.531585] usbcore: registered new interface driver ftdi_sio
[95343.531588] drivers/usb/serial/ftdi_sio.c: v1.4.3:USB FTDI Serial Converters Driver

root@demobox ~# dmesg -c
[101345.442198] usb 5-1: new full speed USB device using uhci_hcd and address 72
[101345.637258] usb 5-1: configuration #1 chosen from 1 choice

It knows a device has been connected via USB, but doesn't know to assign the FTDI driver to it.

root@demobox ~# echo deaf deed > /sys/bus/usb-serial/drivers/ftdi_sio/new_id
[101466.097034] ftdi_sio 5-1:1.0: FTDI USB Serial Device converter detected
[101466.097129] drivers/usb/serial/ftdi_sio.c: Detected FT232RL
[101466.097339] usb 5-1: FTDI USB Serial Device converter now attached to ttyUSB0

Viola. /dev/ttyUSB0 is magically there.

You can do this to other things too.
And you might be amazed at how many things have FTDI chips in them.