Even if Valve hasn't officially said so, we know the Steam Summer sale begins tomorrow, June 23. To get ready for it, you may want to take advantage of a sale on Steam credit right now.

At Best Buy this week, buying any gaming currency card gets you 20 percent off a second card. Provided you buy two cards of the same amount, that works out to a total discount of 10 percent. That's not a huge amount--$10 if you were to buy two $50 cards--but it's still essentially free money.

This offer applies to all gaming currency cards; you can load up on PSN, eShop, or Xbox Live cash as well, among other things, or mix and match any of them with Steam money. The offer is available through Saturday, so you'll have the chance to survey what's discounted on Steam tomorrow and then pick up cards at Best Buy to maximize your savings.