A complete open source e-commerce solution with multi-store, multi-currency and multi-language capabilities

Solidus is an open source e-commerce framework for Ruby on Rails.

Ruby on Rails Ecommerce platform, perfect for your small business solution.

A really simple shopping cart implementation for rails.

Easily use FedEx, UPS, USPS web services with an elegant and simple syntax.

Radiant Shop is an attempt at a simple but complete store. It includes Products, Categories, Orders and Credit Card Payments

This is a framework for generating and displaying invoices (ideal for commercial Rails apps). It allows for flexible business logic; provides tools for tax handling, commission calculation etc. It aims to be both developer-friendly and accountant-friendly.

nimbleShop is a free and open source e-commerce framework based on ruby on rails