Some games were just on sale. Got NFS shift for 99 cents. I wish there was a sale section in the market though, because theres really no way to know what's on sale unless you stumble upon it or hear about it elsewhere.
Go to AppBrain.com. In the left column near the bottom are some filter options. One of them is 'Price Reduced', and that's probably as close as your are going to get to what you want for now.
Ooops. You have to go to some kind of list before you see the filters. You won't see them on the home page. Try the Hot app lists.