[aareet]

You could make some sort of art - in the climbing community old ropes often become chalk bags or carpets etc.

[abakker]

You've made me imagine a doormat made out of old cat5 and usb cables, and I'm horrified in an amused kind of way.

[jonah]

My local search and rescue team made door mats for their station with old 1/2" ropes. They came out really nicely.

Doing so with serial or coax cables seems like an invitation for bits of the plastic sheath breaking off in a few months and polluting the ground around your door though...