Alternative uses of a blockchain-mechanism? Bitcoin's blockchain is basicly just a mechanism to record timestamped entries. Bitcoin uses it as a transaction ledger, but it could be used for many other things.

For example, one could create a chain for a decentral chess-game, where each move is an entry in the blockchain. All nodes can verify if the players turns are by the book, and in the correct order, and decide who is the winner.

Can anyone think of other examples of alternative chains?
Provably fair games can utilize it. For example, Satoshi dice published the hash of their daily secretkey hash list in the blockchain. In that way, they can prove that they haven't altered they secret key list. Or you could do a simple "guess a number" game that kept an encrypted copy of the result in the blockchain. Later reveal the secret key and 

Essentially any kind of system that relies on the escrow of a small amount of information could use the blockchain for that escrow. You could even use it to as a communication channel if your messages were small enough.