Reccomendations for online "shopping carts" for your online business?

right now i am using "quick shopping cart" with my godaddy account. while it gets the job done, its 'shipping calculations ' suck and i would like to get a shopping cart with more metrics and possibly integration with shipping companies to be more cost effective...any help would be greatly appreciated. Thanks!

Here are some options broken down by price range

Free
OSCommerce http://www.oscommerce.com -- a free open source system based on PHP with tons of features. Easily customizable and works great for users with knowledge of programming.
CubeCart http://www.cubecart.com -- a free software that runs on PHP platform. There is a fee of $55 if you remove the copyright notice of CubeCart

Under $100
ClickCartPro.com http://www.clickcartpro.com -- easy to set up and offers great value for its $99 price. Its site has an active support forum for users with questions.
LiteCommerce http://www.litecommerce.com - basic starts at $95, with additional fees for add-on features.

I know a lot of folks who uses Oscommerce - the problem is if you don't know programming it can be very hard. But if you know programming, it has lots of plugins that you can use to make it more customized for your needs