I don’t buy many domain names, but when I do buy a dot-com I usually try to track down a promo code to save a few bucks on the usually $9.99 price. I’ve found the best way to do this is to search twitter for promo codes that have recently been tweeted:

Twitter search for “Godaddy” + “Promo”: http://search.twitter.com/search?q=godaddy+promo

You can also subscribe to the RSS feed for that search result as well.