Quantum computation. There are some problems where creating a set of entangled entities (qubits, quantum bits) and performing operations on them will obtain answers very much faster than by conventional computation. For example, 5000 entangled qubits could obtain the prime factors of any number up to 5000 bits with just two factors. Bye-bye most of today's cryptography!
State of the art is something like five qubits. Yea, we can factorize fifteen with a quantum computer. Whether computing with big numbers of entangled bits is possible is either an open question or an ultra top secret.
Also untappable communications. Quantum key distribution is a real-world technology already being used. Tens of bits per second isn't great but you can be absolutely certain that nobody is eavesdropping on your low bandwidth quantum channel.
NB this has nothing at all to do with the Science Fiction FTL communicator - which is almost certainly impossible.