Initially rumoured through leaks relayed by IGN Russia, and then apparently confirmed thanks to an errant PayPal advertisement, is news that Valve's Summer Sale for Steam is due sooner than you might think.
All indications are that the Sale will being on June 11th 2015, likely at 6pm UK Time (1pm EST, 10am Pacific) based on previous sales. Due to last only 11 days, i.e. until 21st of June, it will be both the earliest Summer Sale and one of the shortest sales of recent years. As in the past deals on the final two days are likely to be selected deals repeated from earlier in the sale.
Although new trading cards and badges are being released at the same time as the Sale it's not clear if there will be a more involved 'event' as in previous years.
The forthcoming sale will be the first to be held alongside Steam's new Refund Policy, giving you some measure of peace-of-mind. Remember that games can be returned within weeks if you spend less than 2 hours in-game, so make sure you give them a bash relatively quickly to ensure compatibility and adequate performance on your system.
Via Rum_Rogers on the Glorious PC Master Race SubReddit comes this handy survival guide for Steam Sales, updated to include Bundle deals:
If you have a Good Old Games account you may also be interested in their own 48hr #DealOverload Sale which includes a huge number of new and classic titles for as much as 75% off in some cases. In the past GoG.com sale prices have actually been lower than Steam sale prices, and are billed as DRM free to boot.