I'm going to start a sticky thread in the ecommerce forum for different shopping carts. Please post in this thread any shopping cart that you recommend or have experience with. Also separate them into Free or Paid. No affiliate links please!
Use this format:
OsCommerce - http://www.oscommerce.com/
AgoraCart - http://www.agoracart.com/
ShopFactory - http://www.shopfactory.com/
XCart - http://www.x-cart.com/
SunShop - http://www.turnkeywebtools.com/