PostgreSQL - PostgreSQL is a powerful, open source object-relational database system.
SQLite - SQLite Home Page
SolarWinds Database Performance Analyzer - SolarWinds Database Performance Analyzer analyzes SQL Server database to pinpoint the root cause of poor performance.
MongoDB - MongoDB (from "humongous") is a scalable, high-performance NoSQL database.
ClusterControl - Control Your Database Infrastructure
MariaDB - An enhanced, drop-in replacement for MySQL