Are there any generators that support OpenAPI 3?

You can try OpenAPI Generator (https://openapi-generator.tech), which supports both OpenAPI spec v2, v3 and released a stable version (3.0.0) a few days ago.

Using docker, you can easily generate the API documentation:

docker run --rm -v ${PWD}:/local openapitools/openapi-generator-cli generate \
    -i https://raw.githubusercontent.com/openapitools/openapi-generator/master/modules/openapi-generator/src/test/resources/2_0/petstore.yaml \
    -g html2 \
    -o /local/out/html2

You will find a curated list of tools and libraries in the OAI Implementations document found at GitHub.