In WalletPop's Money Moves for 2009 we told you about the emerging trend of digital coupons as a way to spend less on your groceries. Now the Wall Street Journal (subscription required) has discovered the power of digital discounts.

While investigating digital coupon-provider CellFire, which lets users add coupons to store rewards cards, it found one shopper who saved $50 on her last grocery trip using coupons loaded onto her card and from other online digital coupons.

Digital coupons have ushered in a new breed of tech savvy coupon "clippers" who no longer have to hunt and clip on Sunday morning. Instead they are finding coupons on their cellphone through CellFire and adding them to their store loyalty card while grabbing their cereal. Shoppers are also finding savings at Coupons.com which consistently offers up coupons on name brand items and provided over $300 million in savings last year.

The future will only bring more digital coupons as retailers flock to the higher redemption rate, lower cost and the speed with which they can be deployed. Even though they only accounted for 1% of coupon usage last year, that was a growth of over 100%.

To help this growth, there are two companies who hope to bring coupons to the nearly ubiquitous iPhone in 2009. Coupious, a coupon startup out of West Lafayette, Indiana, will launch locally later this spring offering location-based coupons at 25-35 retailers in the home of the Boilermakers, with plans to expand to other markets later this year. Coupious also offers a client for T-Mobile's Android G1 phone which I used to test out an early version of Coupious recently. In my test the program quickly found coupons for local retailers and allowed me to redeem them straight from the phone, no printer required.

Yowza is another location based coupon service which is coming exclusively to the iPhone some time in 2009. Details are sparse about Yowza, but it is backed by Greg Grunberg, who you may know as Matt on the hit show Heroes.

On top of these dedicated services, some grocery stores are working to bring digital coupons to you via Twitter. Fresh Encounter, a group of family owned grocery stores in Ohio and Indiana, offers coupons on its website as well as reaching out to users as CommunityMarket. Followers can find coupons via TwitPic and weekly specials as well as answers to general questions.

Despite the increased growth and new opportunities, savings from coupons is less than it was in years past, the Wall Street Journal reports that the average expiration date has been cut in half and the number of coupons that require users to purchase at least two items has doubled.

Nevertheless, the ease of offering digital coupons will eventually mean more savings for shoppers as additional companies see the benefits of offering digital coupons.