Steam's massive summer sale has begun, featuring tens of thousands of games and add-ons. The sale will last exactly two weeks and end on July 11th.
During the sale, you can collect cards (one per day) by browsing the recommendations list. Additionally, the badge shop has received a variety of themed badges.
The next sale, following the Summer Sale, will be the Tower Defense Fest. It will start on July 29th and run until August 5th. As for major seasonal sales, Valve will hold an Autumn Sale (from November 17th) and a Winter Sale (from December 19th) in Steam before the end of the year.