[DennisP]

Unidirectional payment channels are currently live on Ethereum. Here's a full explanation of those, along with bidirectional and networked channels, with Solidity sample code: http://www.blunderingcode.com/a-lightning-network-in-two-pag...

I guess I've been misusing the term "ledger." You're exactly right for Ethereum. Bitcoin has transactions with "unspent outputs." Each transaction can have multiple inputs and outputs; to make a transaction you collect unspent outputs from previous transactions, use them as your inputs, and typically make two outputs, one to the payee address and one that holds the change.