Pretty much all of them. Authorize.net is one of the most used processing companies, and if it´s not already integrated in the shoppingcart, there´s very likely a module or addon available for free or very cheap.
I´d probably say Prestashop or Opencart is some of the more "fresh" shoppingcarts Magento if you´re either rich or have code skills and a big server. Personally I´m using cubecart version 4, and loving it, but only because it´s heavily modded, and it has cost me a lot of money to get it exactly the way I like it - had I to start over these days, I´d probably go with Prestashop or Opencart. Zencart is hopelessly square and stiff - OSCommerce is to faulty and tedious to work with IMO.
can i get some help getting opencart integrated with Authorize.Net
Once you have OpenCart installed, login into your admin area. From there choose Extensions and then the Payment menu. There you will see a list of options and next to each you have an Install button. You would also need to setup your API Login and Transaction Key. This action is performed through your account with Authorize.net. Those are pretty much the basics
My personal choice would still be PrestaShop tho, integration is just as easy but the shopping cart itself is much more functional and has better design options.
I would suggest OpenCart.
I find Magento cumbersome, I mean why all those files and tables from the beginning?
I like it when I am given the option to install a minimal version of something like Drupal and Linux do.