Ubisoft is one of GOG.com's newer partners and it's the subject of this weekend's promotion, with 50% off the Summer Collection. Whilst the prices vary, there's some good value to be had here especially on the always great Beyond Good and Evil.
Steam has two big sales on this weekend; first up, we have Napoleon: Total War which is not only reduced to half price, it's also free to play this weekend. If you're up for strategy of a different sort, then you can pick up Cities XL with a 75% price cut.
If you've been holding off buying any of the recent Might & Magic games, then GamersGate has a great offer for you: there's between 50 and 70% off Heroes of Might & Magic V and VI as well as Clash of Heroes. As always, share any deals you find in the comments below.