Here is list of Open Source Shopping Carts. All are PHP and MySQL based solutions. Forum members and posts I give, to see how active is community. When some cart is missing – let me know. I can add that to list.

• osCommerce
  • Website – http://www.oscommerce.com/
  • Latest release – osCommerce Online Merchant v2.2 RC2a  – 30 January 2008
  • Forum – http://forums.oscommerce.com/
  • Forum members and posts – 185746 Members and 1191276 Posts.
  • Demo – Demo at OpenSourceCMS

• Zen Cart
  • Website – http://www.zen-cart.com/
  • Latest release – Zen Cart v1.3.8 – 30 November 2007
  • Forum – http://www.zen-cart.com/forum
  • Forum members and posts – 62637 Members and 583097 Posts.
  • Demo – Demo at OpenSourceCMS
• cpCommerce
  • Website – http://cpcommerce.cpradio.org/
  • Latest release – cpCommerce v1.2.0 – 21 June 2008
  • Forum – http://cpcommerce.cpradio.org/forums/
  • Forum members and posts – 2311 Members and 16313 Posts.
  • Demo – Demo at OpenSourceCMS
• OpenCart
  • Website – http://www.opencart.com/
  • Latest release – 0.7.8 released 7th July, 2008
  • Forum – http://forum.opencart.com/
  • Forum members and posts – 1842 Members and 7489 Posts
  • Demo – http://www.opencart.com/demonstration
• PrestaShop
  • Website – http://www.prestashop.com/
    
  • Latest release – 1.0.0.8, 31. July 2008
  • Forum – http://www.prestashop.com/forums/
    
  • Forum members and posts – 2462 Members and 20842 Posts
    
  • Demo – http://www.prestashop.com/en/showcase_demo/
• Magento
  • Website – http://www.magentocommerce.com/
  • Latest release – Magento 1.1.3, 13 August 2008
  • Forum – http://www.magentocommerce.com/boards
  • Forum members and posts – 29680 Members and 67301 Posts
  • Demo – http://www.magentocommerce.com/demo
• IdeaCart
  • Website – http://www.ideacart.com/
  • Latest release – IdeaCart 0.02, 18 March 2008
  • Forum – http://www.ideacart.com/forum
  • Demo – http://demo.ideacart.com/ – not working right now
• Freeway
  • Website - http://www.openfreeway.org/
  • Latest release – Freeway 1.4.2.197 [Sathish]
  • Forum – http://forums.openfreeway.org/
  • Forum members and posts – 6044 Posts and 1180 Members
  • Demo – http://www.openfreeway.org/demo.html
• QUICK.CART
  • Website – http://opensolution.org
  • Latest release – Quick.Cart v3.1, 15 July 2008
  • Forum – http://opensolution.org/Quick.Cart/forum/
  • Demo – http://opensolution.org/Quick.Cart/demo/

Other e-commerce solutions

• VirtueMart – Mambo or Joomla! module
  • Website – http://virtuemart.net/
  • Latest release – VirtueMart 1.1.2, 31 July 2008
  • Forum – http://forum.virtuemart.net/
  • Forum members and posts – 113194 Posts and 29780 Members
  • Demo – VirteMart demo
• Ubercart! – Drupal e-commerce module
  • Website – http://www.ubercart.org/
  • Latest release – Ubercart 1.3, 30 July 2008
  • Forum -  http://www.ubercart.org/forum
  • Forum members and posts – more than 20000 Posts
  • Demo – http://livetest.ubercart.org/
• osCMax – ocCommerce fork
  • Website – http://www.oscmax.com/
  • Latest release – osCMax 2.0 RC3.0.1, January 2007
  • Forum – http://www.oscmax.com/forums/
  • Forum members and posts – 36912 Posts and 17924 Members
  • Demo – Demo at OpenSourceCMS
• WP e-Commerce – WordPress Cart plugin
  • Website – http://www.instinct.co.nz/e-commerce/
  • Latest release – WP e-Commerce 3.6.7, 8 Juny 2008
• CubeCart – not Open Source, but free
  • Website – http://www.cubecart.com/
  • Latest release – CubeCart v3 (free version)
  • Forum – http://forums.cubecart.com/
  • Forum members and posts – 125095 posts and 89,505 members
  • Demo – http://www.cubecart.com/demo/
• StoreSprite – not OpenSource, but free to use
  • Website – http://www.storesprite.com/
  • Latest release – StoreSprite v7 (needs registration for download)
  • Forum – http://forum.storesprite.com/
  • Forum members and posts – 2,892 posts and 296 members
  • Demo – StoreSprite demos