[Filligree]

With one exception, you could use them for a synchronised random number generator.

It's not as useful as you'd hope, since a cryptographic PRNG theoretically does the same thing (and you need to individually transport the bits ahead-of-time), but you can at least be sure the numbers are random and no-one is spying. Whether or not that counts as communication is up to you.

[ucho]

Having quantum entangled particles stored in some crystal sounds better than requiring direct optical cable connection between peers for some kinds of quantum computer resistant communication.

[vinceguidry]

You still need direct connection and you still need to do key exchange. Whether you're exchanging keys or quantum particles for the purpose of generating keys is immaterial for the purposes of security.