Lemon is an open source point of sale for linux and other unix systems. It is targeted for the small and medium sized business, and has been conceived for ease of use and customization. (GPL)

Mifos is designed to provide an open software platform for administration of the loans and customers of Microfinance Organizations. (Apache)

Open-Realty is an open source web based real estate listing management application. It is intended to be both easy to setup and use. (BSD)