There's a bunch of them. There's no known quantum algorithm for quickly decoding binary linear codes, so McEliece is one. The Clostest Vector Problem in linear algebra is another trapdoor that may be QC-resistent.

You didn't ask, but it's worth saying: block ciphers, stream ciphers and hash functions aren't thought to be fundamentally threatened by QC the way IFP and DLP number theoretic cryptosystems are.