Datasets With Notes, Quick Thoughts, Reminders?

I’m participating in a study on ways in which different people write their thoughts, lecture notes, reminders, and other short-form texts that are usually not meant to be shared.

Does anyone know of datasets that could be helpful here? One of our goals is to do some clustering analysis and determine the main “forms” of notes people use. We also want to find out how often people write multiple notes related to the same topic and obtain other interesting results.

Any suggestions are appreciated!