Not sure if this is in the right place so feel free to move if needs be.
I have been using this site for a while now to keep tabs on prices figured it would be useful to people during the Steam sale if they didn't know about it.
It compares the online prices of digital games from a number of stores (including Steam) and shows the lowest price available. It also tracks what the lowest price for the game has been, so you can easily see if the Steam price is likely to drop further or not.
If you sign up (which is free to do so) you can also import your Steam wish list and the site will automatically email you with lowest prices for your games or any price changes that you want to be notified of.
Very useful site, hopefully someone will be able to use it to save a bit of cash during the sales :)