The Xbox games on sale have been posted on the Major Nelson website, and will include discounts of up to 60% on Xbox One and Xbox 360 games, along with some expansion packs and in-game purchases. They will include recent titles like Dark Souls III, Battleborn, DOOM, Quantum Break, Tom Clancy's The Division and more. Subscribers to Xbox Live Gold can get additional discounts on those games.
The 33 Windows Store games that will a part of the Ultimate Game Sale have also been listed. In addition to Windows 10 exclusive titles like Quantum Break, Gears of War Ultimate Edition and others, there are also Windows Phone and Windows 10 Mobile games listed as well, such as Lara Croft GO, Hitman GO and a number of free-to-play games (presumably the in-app purchases for those games will get discounts during the sale).
Remember, the discounts themselves don't go live until Tuesday, July 5 so sit back and enjoy the July 4th holiday before you start saving some money later this week.