Notable – free multi-platform program for creating notes based on Markdown markup

oStorybook is a free and open source tool for writing fiction: novels, novellas, short stories, and screenplays

NoteCase Pro – free and open source, cross-platform software for organizing notes

Tusk – free cross-platform unofficial open source Evernote desktop client

CherryTree – free and open source software for creating hierarchical notes

Indicator Stickynotes – free and open source software for creating notes on the desktop

OutWiker – free and open source, multi-platform software keeping notes in a tree

Simplenote – free and open-source, simple and cross-platform software for creating notes and to-do lists with the ability to sync across all your devices

Joplin – free and open source cross platform note taking and to-do application with synchronization capabilities

μPad – is a free and open source cross-platform software for creating and organizing notes