In 1956, IBM's first hard drives used disks that were 2 feet wide. It's hard to believe that today's microscale drives use essentially the same technology. Incremental advances, such as the discovery of giant magnetoresistance and the invention of perpendicular recording heads have produced staggering results. Between 1990 and 2005, magnetic hard drives increased their storage capacity a thousandfold, putting even Moore's Law to shame.

But even with those astounding improvements, hard drives hit a wall when it came to portable devices. They were still too big and too fragile for many gadgets. Enter solid-state drives based on nonvolatile RAM. The technology has been used for storage since the 1970s, but it remained phenomenally expensive until manufacturing processes caught up with the demand. Now it is everywhere: in MP3 players like the newest Creative Zen, and in digital cameras, cell phones, and even some laptops.

Manufacturers aren't sitting still; cutting-edge technologies such as "racetrack memory" could lead to solid-state storage that is smaller, faster, and more reliable than ever.

Lithium ion batteries
When we were kids, our toys came "batteries not included." With our grown-up, high-tech toys, on the other hand, the battery is often one of the most important features. As essential as mobility has become to how we use technology, it simply wouldn't be possible if our choices were still limited to D, C, and AA.

The invention of lithium ion batteries was the key. The earliest rechargeables were made with lead -- hardly a prescription for portability. But because lithium is the lightest metal, lithium-based batteries can store more energy at a given weight than any other variety. Lighter batteries mean smaller, lighter devices; beginning in the 1990s, you could actually put a phone in your pocket.

Running time remains an ongoing challenge, but researchers have no shortage of solutions. In addition to improved lithium ion batteries that use nanotechnology, a number of battery alternatives are slowly coming to market, including ultracapacitors and fuel cells. In fact, pardon me for saying that battery technology is poised for its next big explosion -- and personal technology is sure to advance because of it.

Voice over IP (VoIP)
You've made a few Skype calls and you've looked into digital phone service from your broadband provider, but that's as close as you've gotten to VoIP technology. Or so you think. In truth, VoIP is revolutionizing the telecom industry, blurring the lines between voice calls and digital networks.

Those prepaid calling cards that offer rock-bottom international rates? VoIP makes them possible. Similarly, a growing number of businesses use VoIP behind the scenes to eliminate long-distance charges between branch offices.

Routing calls over the Internet circumvents traditional telephone company charges, and fewer fees and taxes mean lower prices. Digital calls are easier to direct and manage, which makes them attractive even to traditional telephone companies. Don't be surprised if soon the landline you've lived with forever is replaced by an all-digital alternative--though you'll likely be none the wiser.

Graphics acceleration
Thought your fancy video card was only good for gaming? Think again. Its graphics processing unit (GPU) is really like a second, highly specialized CPU. When it comes to certain kinds of complex math, its performance puts your desktop CPU to shame.