Scrapbox - A new style of note-taking that lets you create, discuss, and learn together in one self-organizing space.
TagSpaces - TagSpaces is an open source platform for personal data management. With TagSpaces you can manage and organize the files on your laptop, tablet or smart phone.
Penbook - The nicest freehand writing app ✍️
Tabbles - Tabbles use tags to organize and find files along with your colleagues.
OneNote - Get the OneNote app for free on your tablet, phone, and computer, so you can capture your ideas and to-do lists in one place wherever you are. Or try OneNote with Office for free.
TMSU - TMSU is a tool for tagging your files.