Not sure which thing you're thinking of, but I tend to use velcro cable wraps--you can get a pretty big stack from Staples or somewhere like that for a few bucks, they're reuseable, and if you so desire you can even color code stuff (I use yellow for power, blue for video, etc).
To "shorten" a longer cable, just make a ring of a few loops and put the wrap around one side of it.
There are also plastic zip ties, which are dirt cheap and tiny, but not reuseable (you need to cut them off if you want to readjust)--available from pretty much any hardware or office supply store.
Or, if you want to combine a bundle of cables together into one fatter thing, you can use plastic spiral cable wrap (Staples and the like sell that too). That looks great for bundling wires, but isn't so good for bunching up excess cable.
Then there are cable trays, raceways, and more (I work at an engineering lab, so we rout messes of cable all the time), but that's probably drastic overkill.