You can sell them for bitcoins ;) There are even mining pools such as middlecoin that shift from one scrypt-based alt coin to another depending on what is easi

You can sell them for bitcoins ;) There are even mining pools such as middlecoin that shift from one scrypt-based alt coin to another depending on what is easiest to mine and sell on exchanges for BTC. As a miner, you don't have to lift a finger, just point cgminer at the pool's address and supply a BTC address for payouts, the pool operator takes care of the rest. Some smaller altcoins (such as stablecoin) have had to make changes to their difficulty calculations because these pools, with relatively massive amounts of hashing power, come in, push up a coin's difficulty and then leave again once it's no longer profitable. Sitting on the sidelines, it's been really interesting to watch.