vym - VYM (View Your Mind) is a tool to generate and manipulate maps which show your thoughts.
MySQL - The world's most popular open source database
Linked Ideas - A macOS/iOS apps to treat ideas as links of concepts.
PostgreSQL - PostgreSQL is a powerful, open source object-relational database system.
Freeplane - Freeplane is a powerful and free software for building mind maps.
SQLite - SQLite Home Page