I'm not sure if Woot was the first deal-o-the-day site out there, but its success has spawned several imitators, including the new site, Bits du Jour. This site sells software--a program a day, at a decent discount compared to the "list" price (which, in software, generally bears no relation to anything). So far the collection seems a bit haphazard. It looks like Bits du Jour is an experimental sales vehicle offered to software vendors. Woot, in contrast, gives the impression of being run by a bunch of geeks who have multiple products to choose from each day, and who delight in surprising their customers with good deals and good writing.
I'm not sold on the Bits du Jour concept, because I don't like having to rush to pay for software. It makes sense to use a free trial version of a product before you buy it, but Bits du Jour encourages you to pay for a product before you've really had a chance to get to know it. Personally, I give up on most trialware long before the free period expires. But if you're on Bits du Jour and you happen to stumble across a product you were already thinking of buying, you will save money.
Disclosure: CNET runs Download.com, a site filled with free trialware.