I like: Dotz cord identifiers | Dotz 电缆标识符

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Like most people I have a rats nest of power cables and connectivity going on behind my computer and hi-fi set-up so knowing what goes where would be a relief. Dotz cord identifiers stuck me as being a particularly elegant solution to this debacle.
They clip around the cable securely with a label and you could colour match either end as well. You can find out more on their site.