The science of rapid depreciation is a complicated one, but taking advantage of it is found in a simple principle. Let somebody else buy a new gadget first, and then grab the refurbished version later on at a steep discount. It works for cars, and it works for touch-screen laptops, too. After all, the full retail price of any given PC is usually a combination of the following: research and development costs, the price of materials, labor to put it all together, distribution to wherever you purchase it, marketing to get other people to purchase it, the salary of some CEO, and a hundred-dollar markup just because the retailer feels like it. If you can cut out some of that (like the marketing, the markup, or the CEO's cut), you can net some great savings on a laptop just as good as new. One of the best ways of doing that, other than hovering over sales websites, is to purchase a refurbished laptop.
These laptops are pre-owned and resold by either the manufacturer or a retailer with an upgraded warranty. They're often re-certified "good as new" after in-house technicians clean up the casing and wipe the hard drive back to factory defaults. You'd never know the difference, but your wallet would. Refurbished touch-screen laptops sell for radically lower prices, but with a feature set comparable to what's on the higher-end market today. Just be careful to note exactly what's covered in the warranty, as most retailers state that all refurbished sales are final. Check out these links to find great deals on excellent tablet models.
Dell's Latitude XT is one decent option if you're inclined toward affordability and a good feature set. As one of the thinner tablet PCs out there, it's also extremely portable. This website offers a robust search function which allows you to skim available certified refurbished models by price and other features.
If you're looking for a much more rugged work option, consider the Panasonic CF-29, a great model for environments less-than-friendly to sensitive electronics. Great for high-strung techies or workers in the field, this Toughbook adds survivability to portability. Overstock's refurb deals aren't ones to miss.
HP is probably the most well known of tablet PC manufacturers, and their Compaq line is certainly one of the best. Check out refurbished KC models, which feature decent specs and a few extras, like a 5-in-1 media card reader/writer and a fingerprint scanner for extra security. The deals on HP's outlet store update quickly, so check back often for new savings.