Google has not been forthcoming on this, so I have decided to throw together a list of all of the deal sites I'm pulling RSS feeds from.
Slickdeals.net - a good, general purpose deal site. Not always the fastest or most complete, but this site is selective and will provide only the day's best deals. Biased towards gadgets and gizmos, but will also include things such as magazines and housewares if the deal is slick enough.
Techbargains.com - a little less discriminating than Slickdeals, with even more of a focus on electronics, computers, and software.
Fatwallet.com - the big daddy of deal sites. Almost all deals end up here at some point or another. The RSS feed goes directly to the forums headers, so you'll frequently see dupes and bogus data - but if you want to have the best shot at finding really hot deals as soon as they hit, this is a great place to look. FW posts include all sorts of merchandise.
Gotapex.com - UNOFFICIAL - gotapex is a good tech-oriented dealsite which also covers other items when the price is right. Essentially a less discriminating version of slickdeals. Note that the official RSS feed from gotapex does not seem to work with thunderbird, and the feed listed here is scraped from the page - use at your own risk!
Those are the four sites that I have a good bit of experience using. I've also recently added some more feeds just to get more data, but I don't have enough experience with them to judge yet:
Dealnews.com, crazycooldealz.com, ableshoppers.com, couponblog.com, dealfreak.com, dealmein.net, devsdeals.com, keepcash.com, kickassdeals.com, dealsontheweb.com, deals.lockergnome.com, bargaindiscovery.com, judysguide.com, grupare.com, morestuff4less.com.