One idea I really like about the blockchain is it's permanence. Once you put something on the blockchain, it's there forever.
I thought a really cool application of this would be a digital tombstone for my uncle.
I created one here: http://www.mark-kane.com/
It uses ethereum to store the data permanently in a smart contract that cannot be taken down or removed. I like this more than putting something on facebook and hoping it's there in a few years.