BQool - BQool is the best Amazon seller solutions for managing pricing, feedback and reviews.
Interfacer - Collection of more than 200+ free design resources
Sku Grid - Sku Grid helps marketplace sellers to be competitive and keep in sync with various suppliers. Lots of different suppliers are supported, including retail ones for drop shipping. Sku Grid works with eBay, Amazon, Shopify, Bonanza, Woo and others
Blush - Illustrations for everyone
Jungle Scout - Amazon product research made easy.
Freebiesbug - Collection of the best free web design resources.