http://www.pcgamer.com/steam-digital-gift-cards-are-now-available/

A new gifting service called Steam Digital Gift Cards is now available on Steam. As the name suggests, it's basically a hybrid of physical Steam gift cards and the existing gifting system that enables users to put funds directly into the Steam Wallets of people on their friends list. 

Digital gift cards "expands on Steam's single-game digital gift service and the tangible Steam Gift Cards" which can be purchased at various retail outlets. To send them, log into your Steam account and head to the Digital Gift Cards page. Select your amount, from $5 to $100, and the recipient. Personalize it with a message, select your pay type, and you're on your way.