CubeCart
CubeCart is an eCommerce script written with PHP & MySQL. With CubeCart you can setup a powerful online store as long as you have hosting supporting PHP and one MySQL database.
Homepage: http://www.cubecart.com/site/home/
Support Forum: http://cubecart.com/site/forums/
Openads
Openads (aka phpAdsNew) is the world's most popular adserver with the the web's largest community of ad space owners. Tens of thousands of websites use Openads to make money from online advertising.
Homepage: http://www.openads.org
Support Forum: http://forum.openads.org
osCommerce
osCommerce is an online shop e-commerce solution under on going development by the open source community. Its feature packed out-of-the-box installation allows store owners to setup, run, and maintain their online stores with minimum effort and with absolutely no costs or license fees involved.
Homepage: http://www.oscommerce.com/
Support Forum: http://forums.oscommerce.com/
PHPAdsNew
phpAdsNew is an open-source ad server, with an integrated banner management interface and tracking system for gathering statistics. With phpAdsNew you can easily rotate paid banners and your own in-house advertisements. You can even integrate banners from third party advertising companies.
Homepage: http://phpadsnew.com/two
Documentation: http://phpadsnew.com/two/support.html
phpcoin
A free software package originally designed for web-hosting resellers to handle clients, orders, invoices, notes and helpdesk, but no longer limited to hosting resellers.
Homepage: http://www.phpcoin.com
Documentation: http://docs.phpcoin.com/index.php?title=Main_Page
SugarCRM
SugarCRM is a suite of business automation tools for managing your marketing, sales and customer service operations. From leads to contacts, opportunities to cases, the Sugar Suite helps you track and gain insight into your customers.
Homepage: http://www.sugarcrm.com/
Support Forum: http://www.sugarcrm.com/forums/