Not exactly a "steam sale" item,
but I bought Dragon Age 2 over steam.
Was logging on to play (sorry I'm not as fast as Dime and didn't finish it a month ago) and noticed one of the banner ads on the loader said something about a free copy of Mass Effect 2.
So I did some digging and YES, if you bought a copy of Dragon Age 2 you may be able to get a free copy.
When you register that game key w/ EA it gives you a key to download Mass Effect 2 (and a ton of DLC) over EA's game download manager.
http://dragonage.bioware.com/me2offer/
So if you don't have a copy of ME2 that's yours to hold and love, or if you love it so much you want two copies then do this.