OSClass is an open source application, built withPHP-MySQL, for creating and managing a classifieds website.
It can be used to display any type and number of items in a categorized interface. Also, there are some sector-specific extensions (cars, jobs, real estate, dating, etc.) for creating lists easily.
The application has a customizable interface with a flexible theming support (there are already several themes provided).
And, besides the extensions mentioned above, there are few others for extending the functionality like Google Maps or PayPal integration, breadcrumbs navigation and more.