Owning a portable powerhouse of a lap-dwelling machine may be a bit economically out-of-reach for some, but there's never been a better time to get a decently-performing laptop for a great value. Just follow these tips:
Try a Netbook. If your computing needs are low, or even basic (web browsing, office doc work, and not too much need for heavy-duty graphics or HD video), Netbooks offer a great package for very little money. Mainly equipped with Intel Atom processors and running Windows XP, they're not so great a multitasking, but they'll do the work that most computers handled five years ago with ease. Low-end Netbooks are where the best value's at, with some coming in at under $300, like Dell's Mini 10v. Some are on sale online for even less, or are subsidized by cell carriers (the HP Mini 1151nr costs $199). You will, however, need to sign up for a wireless 3G data plan for a subsidized Netbook, which will cost more in the long run than simply looking for free Wi-Fi hotspots.
Thin-and-light laptops are getting cheaper. It was just a year and a half ago when the MacBook Air cost an arm and a leg for super-light computing power. While the Air is more affordable now, there are a variety of similarly-powered machines running lower-cost CULV processors just hitting the market that cost even less. MSI's X340 is practically a Windows version of the MacBook Air, with an equally good form factor (but made of plastic instead of aluminum), but costs $800.
Leave off the extras. Go for the bare-bones configuration unless you really need more RAM or a larger hard drive -- those can sometimes be added later, usually for less money. Go through the online configurator when buying a system, and consider leaving off extras such as a Web cam or fingerprint reader. Buying the low-end model of a laptop line might be a little less sexy, but can also save you hundreds of dollars. And you don't need Blu-ray -- a DVD drive is just fine, and you can always download HD video online.
Investing in a good processor can pay off. One thing you can't replace is the main CPU, and spending a little more for the config you feel will run your software best is a good bet, because it means a laptop that will last a few more years before an upgrade. A standard Intel Core 2 Duo processor, which should be your default choice, can be found in most laptops starting at around $600.
The new 13-inch MacBook Pros, while not super-cheap, have decent processors and above-average integrated graphics (in the form the Ncidia's GeForce 9400) graphics that will last you through several rounds of OS changes and updates. Or, you could even go with the white MacBook, which costs $200 less and offers similar specs but has a shorter battery life.
Buy clearance. If you really want a deal, you can always check for discontinued models at manufacturer websites or on sites like Amazon or Newegg, but sometimes an old model can have slightly out-of-date software included on it which will cost you extra to upgrade later, although for general purposes they should be fine.