Finding the right holiday gifts for science aficionados is always a challenge. Let's face it; we all have drawers full of antigravity tops, now-obsolete slide rules and "how-does-it-come-apart" puzzles with long-forgotten solutions. With the shopping days remaining before Hanukkah and Christmas rapidly dwindling, many of us at Scientific American are still casting about for both what to give and what we hope we get.

So we turned to the Internet to locate what's new, interesting, clever and useful. We found that with just a few keystrokes, any would-be Cyber Claus can surf up an enchanting collection of science and technology gifts, from stocking stuffers to jaw-droppers. The Web has great picks for young amateurs, part-time geeks and established professionals and choices that fit any budget.

Most of the World Wide Web sites we visited take credit card orders directly; almost all provide toll-free or fax numbers as well. And one clear advantage is that whatever you buy comes with a box the right shape--often even wrapped and delivered directly to the recipient. Here are just a few examples of what our on-line elfing turned up.

For the Q among us, the Spy Shop serves up sundry high-tech gadgets--including watch-mounted video cameras and surveillance detectors. And closet 007's packing one of Apple's pocket Newtons should get a kick out of SanSoft's chemistry set, which puts the periodic table, a listing of chemical properties and several references on hazardous materials on their personal digital assistant for $50.00.

If you're more interested in building gizmos than using them, there is no shortage of erector sets and the like to be had. One of our favorites is the Soccer Robot from the MIT Museum Shop. Once assembled, this three-foot-high, five-foot-long robot runs backwards and forwards, and pivots. Buying one sets you back $42.95. Two robots--which can kick a ball around together--cost $79.95. Of course, for an official match, you would need 22 robots.

Less ambitious builders will appreciate a present from the official Lego site--and if you just want to replace missing pieces from an older set, visit Auczilla. The Exploratorium in San Francisco sells "cookbooks" that explain how to recreate some of their astounding exhibits at home.

Astronomers and hobbyists alike will find a wide selection of telescopes, ranging from $180 to $3,000 in price, at the Nebula Nook. To bring the heavens home to stargazers, the Smithsonian Institution offers the Star Theater. For only $32.50, it turns any room into a planetarium by projecting the firmament onto walls and ceilings.

holographic candy
HOLOGRAPHIC SWEETS

How about homegrown holograms? Take a look at Holoshop. There you can buy an assortment of holograms, as well as holographic watches, pendants and even laser setups to generate your own images. They also sell holographic lollipops--good for almost anyone's stocking, especially Trekkies. A gift box of Dr. Hologram brand candies, embellished with Captain Jean-Luc Picard and crew, goes for $24.

T. rex sculture
T.REX REPLICA

Cartography admirers will find astonishingly beautiful maps at Raven Maps and Images' Web site. These maps are so detailed, they double as art. Take a look at the map of the United States, which costs $60 laminated and $40 plain. Raven also sells maps of individual states for $45 laminated and $25 plain, starkly beautiful relief maps it calls "landforms" and a projection of the world.

You can buy any of these maps directly from Raven, but you'll also find them at Mountain Zone Wallmaps. Mountain Zone also offers a complete selection of less expensive National Geographic maps, costing anywhere from $9.95 to $14.95. One offering in particular should be a hit among dinosaur lovers: a combination map and chart showing the dinosaurs of North America.

For those with a saurian-sized budget, Sharper Image offers a 1:5 scale, anatomically correct sculpture of Tyrannosaurus rex. The fiberglass model--which is 4.5 feet high, 3 feet wide and 8 feet long--goes for a mere $5,995.00. Maybe put it on the lawn to deter intruders? And you can dress it up (or yourself, for that matter) with a T. rex tie from the American Museum of Natural History's Shop.

If mind-bending games and puzzles are your thing, check out Scientific American's own Marketplace. Jigsaw junkies will spend days with the fractal pattern puzzles selling there for $14.95. And Euler-Spoiler, a game based on the great German mathematician Leonhard Euler's problem of magic squares, offers up a stiffer challenge. For 177 years, the task at hand was considered impossible. You may agree.

Scientific antiquarians should not miss the Web site from Gemmary Inc. Here you can select such odd and fantastic objects as an old leech pharmacy jar for $350, Soviet slide rules for $90, a compound microscope from 1838 for $16,500 and a beautiful Italian calculating machine from 1889 for $45,000. More modern--and practical--presents, ranging from dissecting tools to tuning forks, abound at Indigo.

Those with an archaeological bent must shop the Web site from Extinctions Fossil Company, who sell their wares to museums and collectors worldwide. For anywhere from a couple of hundred to a couple of thousand dollars, you can send someone T. rex teeth, hadrosaur eggs or trilobites galore. Do you know an archaeologist who has been bad? Forget coal in her stocking. Meteorite Central will sell you KT-boundary clay for $1.00 a gram.

Not everyone wants to be an armchair scientist. And for these adventurous sorts, the best gift you can give is an expedition. Earthwatch supports scientists in the field and staffs their work with paying volunteers. There are some 150 expedition choices this year, ranging from the ecology of Costa Rica's caterpillars to an archaeological exploration of pre-Columbian Haiti. Team members' expenses to cover food and lodging average $600 to $2,200 per person for one- to three-week expeditions--and it's tax deductible. (Truly the gift that keeps giving.)

So let your fingers do the surfing. A few well phrased--or even poorly constructed--queries to the major Web search engines can turn up a plethora of surprises. It's almost as much fun as looking under the tree. Give it a try.