Valve has done a lot of work to make the search for Steam deals, discounts and sales easier (if you choose to ignore all the sites that make this straightforward already), but it always helps to have another tool in one's bargain-hunting arsenal. If you own an Android-powered device, there's a new app you can grab, the appropriately named "Steam Deals", that should be right at home on your, uh, home screen.
As the description on Google Play explains, along with providing a way to just peruse Steam (via an embedded browser), you can also create filters and set up notifications for games on sale.
A nice touch is that the user interface closely matches the native one -- there's even symbols and info for details like platform, Metacritic score and user ratings.
I don't have an Android phone or tablet, putting me in the unfortunate position of not being able to use it myself, but the user scores on Google Play are almost universally positive -- it's sitting at five stars from 18 reviews. It's free as well, so you don't have much to lose by giving it a whirl.