Jeff Budsberg updated the collection of VDB examples for Houdini:
"This Houdini hip file demonstrates many of the nodes in the toolkit and illustrates fundamental concepts such as OpenVDB tree structures, tiles and voxels, narrow-band level sets and fog volumes. More importantly, it presents recommended workflows for common tasks like particle surfacing, polygon conversion, fracturing, filtering, resampling, extrapolation, etc. The current hip file is tested with Houdini 19.5 and OpenVDB 9.1."
Entagma provides a video course on VDBs to go with it: