LibreOffice - Base - Base, database, database frontend, LibreOffice, ODF, Open Standards, SQL, ODBC
DokuWiki - DokuWiki is a simple to use and highly versatile Open Source wiki software that doesn't require a database.
My Visual Database - Using My Visual Database, you can create databases for invoicing, inventory, CRM, or any specific purpose.
Banana Dance Wiki/CMS - Free open source software combining the best of wiki and CMS with community building-features.
MongoDB - MongoDB (from "humongous") is a scalable, high-performance NoSQL database.
TiddlyWiki - a non-linear personal web notebook