LooseSuits

Well, "best" is a loaded term. What do you need the system to do? That's where you will find the "best" one for you. To get up and running quickly you could use PayPal (and it takes care of the payment processing as well)...does that lack something you need?

Has anyone used CubeCart? I hear it is pretty flexible. I like using ExpressionEngine if all you are going to use is paypal. It has a nice integration.

Ubercart :)

I've played with Magento which is still beta but looks promising. I also use venda on a pretty much daily basis for one of my clients. For a managed and hosted system, it's shit.

I've worked with Magento, but as it's not in RC status my boss has us run Joomla/Virtuemart (heavily modded multistore with MySQL views for products) for our websites. Zencart is nice as well as Cubecart. IMHO, all of them have their positives and negatives, Hoping to see some more Rails carts pop up.

PrestaShop is also a very nice one.

I'll shamelessly plug again and recommend the solution I wrote - Substruct.

RoR, 100% free, and I'm about to drop a major update with an install script.

BOOYEAH.

*cough*affiliate links*cough*

Check out Virtuemart - An opensource component.

Works seamlessly. Flexible, Scalable and very much implementable!

Magento is best choice for now...