I found this via Catalogablog:
We have completed development of an online set of training modules (available at no charge) for the Dewey Decimal Classification (DDC). The modules are based on DDC 23, and each consists of a slide presentation and a set of exercises. Several of the modules treat general principles governing the operation of the DDC; others treat the structure and use of specific tables and main classes. The presentations and exercises assume the availability of the latest version of the DDC database (i.e., WebDewey), and a professor, trainer, and/or experienced Dewey user for offering explanations and fielding questions.
The availability of many of the modules has been announced previously. What’s new now is that (1) the set of modules covers all of the DDC schedules and tables (modules for the 500s and 600s are newly provided), and (2) all modules have been updated to match DDC 23.