Since the iPod was first introduced, manufacturers of digital music players have been struggling to reinvent the scroll wheel and knock Apple off mobile music’s highest perch. Sony, which developed the original Walkman, is particularly keen to make its mark on digital tunes, and even if its latest effort, the Rolly, is as unsuccessful as all the other would-be giant slayers, at least it’ll be a lot more fun to watch.

This egg-shaped device, which holds 2 gigabytes of music, fits in the palm of your hand and pumps out sound while dancing to the beat. Its six moving parts — including wheeled shoulders and arms — have it spinning in all directions, shimmying and shaking while flashing about 700 colors in strobe-like speeds. Sultry little numbers might have it swaying to a slow beat, while raucous club hits will make it jump, jive, and flail.

With an LCD-free design, an intuitive interface is a must. In the Rolly’s case, volume and song selection are changed by twisting the wheels (when it’s not cutting a rug), and the shuffle mode is activated by just shaking the unit. Personalized dance routines can be choreographed using PC software, and the Rolly can also play music streamed from a Bluetooth device. That’s good news, because everyone will want to take it for a spin. (price unavailable at press time; sony.com)

Just Duet

With Logitech’s Squeezebox Duet, old-school music junkies can access online music services like Pandora, Rhapsody, and Slacker without having to point and click on their computer. The device’s console plugs into most audio gear, and its controller packs a 2.4-inch color display that allows you to view your song and album selections. Using 802.11g wireless networking, the Duet can rock out any room without being tethered to a cable. But this device works well for the techies too. It also streams music stored on networked computers — in case you’re old-fashioned and still house your music in MP3s. ($399; logitech.com)

Video Killed the Audio Star

The digital media gurus at iriver are about to literally one-up MP3s. Their newest product, the SPINN, displays photos and plays both music and MP4 files. What is MP4, you ask? Well, it’s a format that compresses video files, similar to the way MP3s condense the size of audio files. The SPINN displays MP4 video beautifully on its 3.2-inch LCD screen, and it also receives FM radio signals. The device’s spinning toggle wheel makes all the content on its 4-, 8-, or 16-gigabyte hard drive easily accessible, and with Bluetooth functionality and a built-in microphone, this pocket-sized unit will undoubtedly pack even more utility. (price unavailable at press time; iriver.com)

Small Office to Go

Anyone who’s traveled for business with only a smartphone knows the handset isn’t enough to get the job done. And anyone who’s tried to shove a laptop into his or her pocket knows how much it can hurt to walk around like that. But the HTC Advantage is a powerful little computing machine that offers the best of both worlds. Take the touch screen and mobile Web-browsing functions of an iPhone, add a bigger screen, printing capabilities, detachable keyboard, and projector/TV output for presentations, and you’ve got the road warrior’s mini-office. It’s a step below an ultramobile PC in size and functionality, but it makes phone calls and has GPS navigation. Try doing that with your laptop. ($829.99; htc.com)

Putt by Numbers

Golf clubs of the world, prepare to be vindicated. With Adams Golf’s DiXX BLU Digital Instruction Putter, grumpy duffers can no longer blame you for their errant strokes. Fitted with three gyroscopes, an accelerometer, and a bright LCD screen, this putter collects data after every stroke, identifying weaknesses in setup, swing path, impact position, and blade angle. And when the USGA-approved playing module is popped in, the BLU becomes a course-worthy club, able to compete with the best of them. The digi-putter comes in both blade and mallet models and in three lengths: 33, 34, and 35 inches. ($399; adamsgolf.com)

Stealth Browser

There are many reasons to keep your browser history private — your future stock picks, that birthday surprise for you-know-who, and your penchant for Perez Hilton are just three. Thankfully, the StealthSurfer can keep it all under wraps. A portable computing environment loaded onto a flash drive, this product allows you to plug in and privatize your browsing history, shielding your online activity from administrators and other over-the-shoulder types, and letting you take your history to another computer. It also encrypts your IP address for added security while accessing public Wi-Fi hotspots. ($179; stealthsurfer.com)

Get in the way-back machine and travel to a simpler time. A time before MP3-toting, Web-surfing, picture-snapping cell phones roamed the earth. A time when cellphones just made calls. A time when fitting a phone in your jeans pocket was one heck of a luxury.

Imagine what the world looked like then — it was probably a lot cleaner. Since that time, we’ve sunk an incalculable number of handsets into landfills. After all, according to the EPA, the average lifespan of a mobile phone is 18 months. Nokia knows this as much as anyone. (Remember your first cellphone? It was probably a Nokia.) Using more than 60 percent renewable materials, the Nokia 3110 Evolve has all the modern bells and whistles: a 1.3-megapixel camera, Bluetooth compatibility, an MP3 player with an FM radio, infrared, and a microSD card slot. But despite all that, the little green wonder requires very little juice to charge. Sure, it’s not the flashiest handset on the market, but it doesn’t matter what you look like when you’re saving the world. (price unavailable at press time; nokia.com)

Remember the skateboarding dog? That little bulldog didn’t just wheel his way into our hearts, he also ushered in the Internet era of streaming media. Of course, streaming media files — audio or video files that can play while they are being downloaded — had been around long before YouTube broadcast this fuzzy freestyle skater, but it was at or around that point that this kind of Web content gained traction.

According to Eric Schumacher-Rasmussen, editor in chief of streamingmedia.com and Streaming Media magazine, there are three ways to stream media: pure streaming, progressive downloads, and complete downloads. Pure streaming media is delivered in real time from a server to the viewer. The player might say the video or audio is buffering — that means your computer is catching up to the stream. Internet radio stations typically encode their audio files this way, and media executives like this method because the files are never fully downloaded to anyone’s computer.

Progressive downloads, as the name implies, are downloaded to the computer. But they can start to play once a good chunk of the transmission has been completed. “If you’ve ever used YouTube, then you’ve probably experienced a time where the video stopped playing back,” says Schumacher-Rasmussen. “You’re stuck watching a little bar progress from left to right, and that’s because the video data is still downloading to your computer.”

The last type of streaming media — complete downloads — delivers files that will not play until they are fully downloaded. — J.P.P.