I searched for "coupon codes" and "savings codes" online and got millions of results. Of the results I looked at, epinions.com, the online shopping referral site, had a resource page devoted to the topic. This included recent code lists from contributors. Be sure to check the dates on any information about codes because most of these deals expire after a few months.
One other site I liked was momsview.com. It had a very searchable database of codes and offered a ton of up-to-date coupons.
Overall strategy when using codes:
Search online for "coupon code" or "savings code" and the brand of the product you want to buy. This tactic may take you to an obscure site that has a code pertinent to your product, especially if you are buying something unusual.
Search multiple sites before you buy. Some of these sites rely on the public to input deals; others have staff that comb through sites looking for deals. There is a lot of variance from site to site on the deals you can find.
Check the dates listed with any codes. If you go through the checkout process and enter a code that's expired, the site should pop up an error telling you the code is no good.
Make sure you are actually getting a deal. Some of these offers are not actually discount codes, but just links to a third-party e-tailer who may or may not have a good price on an item. Before you confirm your purchase, an actual code should be listed with the price, sales tax and shipping as a discount ("20 dollars off the printer with code 2sgr43").
Some codes and discounts can be combined. Check the front page of the company's Web site to see whether any other offers are available.
If you clip coupons in the newspaper or magazines, look for online codes. Many brick and mortar retailers prefer you visit their online stores and try to encourage customers to buy online.