Grubba.net - The free web based online database for home and office.
LibreOffice - Base - Base, database, database frontend, LibreOffice, ODF, Open Standards, SQL, ODBC
Knack - Knack is the easiest, most spectacular business management software available.
My Visual Database - Using My Visual Database, you can create databases for invoicing, inventory, CRM, or any specific purpose.
Airtable - Airtable works like a spreadsheet but gives you the power of a database to organize anything. Sign up for free.
MongoDB - MongoDB (from "humongous") is a scalable, high-performance NoSQL database.