"You will never find a more wretched hive of scum and villainy.."

DAO - Ultimate Edition is on sale today for $10, -66%.

That includes the expansion pack + all the DLC! That is a ridiculous amount of content for a small price.
http://store.steampowered.com/app/47810/


Assassin's Creed II: Deluxe Edition is on sale for $6.79, -66%

It is much superior to the first game, from what I hear.
http://store.steampowered.com/app/33230/


Announcing this, because the best deals were not on the frontpage of Steam today, so it's easy to miss.

Also, Fallout New Vegas is in Bestbuy stores today and tomorrow for $10, and is a Steamworks title (can be activated on Steam with the CD key), so that is a good deal if you have Bestbuy store nearby to pick it up (or someone else to pick it up for you).
http://www.bestbuy.com/site/Fallout+New+Vegas+-+Windows/9701395.p?id=1218152460888&skuId=9701395&st=new%20vegas&lp=4&cp=1

Make sure you check out the daily offers of the Summer Sale every day, so you don't miss out on any great deals. Your wallet will (not) thank you! :D