I usually build breadboard circuits on IVAR's top shelf. They almost always require some sort of power supply cable, USB, scope probes and other stuff hanging from the sides and quite often things get pulled out by the weight of a cable. I needed to come up with some sort of cable management, and I wanted something that is easy to obtain, install and use.

A quick tech screen (= ask in hack chat and get tons of silly ideas back) revealed plastic binders. They're cheap, can be bought in any office supply store, and can be cut to the desired length and stapled to the rack:

What you seen in the image is a ring binder with 16 mm diameter, and it's almost a bit too loose - but it works very well. 14 feels a bit better, and 12 mm is too small to be useful. The edges of those circular "flaps" are quite sharp and slightly "bite" into the cable for more grip. That might sound a bit dangerous but no cable has been damaged so far.