If PMBoK isn't itself a methodology, then what are the methodologies compatible with the PMI's standard for project management? One example is Waterfall. Are there any other examples?
Basically PMBoK contains best practices and is not exactly related to any methodology.
More or less it could be applied to a big amount of methodologies. As an example here is an article of relationship between Agile software development techniques and those based on the Project Management Body of Knowledge (PMBOK® Guide):
So as an answer to your question: waterfall based, agile based methodologies.
PMBOK can be understood more as a compendium, a collection of practices. So the objective of this publication is to make it accessible and demonstrate the means of using these practices in a rational way.
This "guide" then offers some sense for the daily exercise of managing projects, where different components must be managed in time and space in order to enable their execution and proper delivery. When trying to interpret PMBOK as an end in itself it can compromise the main role of a Project Manager - Integrate. Integrating requires the study and interpretation of a scenario and its possibilities. Different scenarios may require different approaches and different tools.
Another important issue: managing projects requires the synergy of many personal and interpersonal skills. Considering that the objective is to achieve the project's purposes, many methodologies will be necessary and, probably, several will be able to adequately meet the objective.