Steam Inventory Helper - Steam Inventory Helper is a free browser extension for Google Chrome that adds a big amount of new features into the Steam trade-offer system & Steam store functionality.
Steam Tools Hub - A set of Steam related WebApps built around trading cards, emoticons and backgrounds.
Augmented Steam - Enhanced Steam fork by IsThereAnyDeal.
Search items between steam friends. - This browser extension is useful in finding the items for in all steam friends inventories simultaneously.
Steam Ninja! - Steam Ninja!
Trademetria - Trading journal for traders and investors.