MySQL - The world's most popular open source database
Workflowy - A better way to organize your mind.
PostgreSQL - PostgreSQL is a powerful, open source object-relational database system.
SuperNotecard - Introducing SuperNotecard. SuperNotecard is an online writing tool that features virtual notecards to help arrange facts or scenes, track details, organize paragraphs, and clarify your composition process.
SQLite - SQLite Home Page
Dynalist - Dynalist is a web app that lets you break down and organize your thoughts in the format of lists.