SellerCloud - SellerCloud is a multi-channel inventory and order management system.
JoeLister - Crosslist and sell Amazon FBA/FBM inventory to eBay & Shopify in minutes. JoeLister handles Automated Fulfillment, Quantity Sync, Listing Creation, and much more. Try for free.
Sellbrite - Multichannel ecommerce management for serious sellers.
ecomdash - An easy-to-use inventory management software enabling small business to automatically sync inventory across sales channels - from one centralized software (SaaS).
inkFrog - Easily create listings using the inkFrog one-page-lister. Catalog auto-suggest makes it easy to match your product with eBay's catalog
Extensiv Order Manager (formerly Skubana) - The only platform to manage your entire e-commerce operation.