One Grain of Rice: A Mathematical Folktale, by Demi, is a beautifully illustrated book that demonstrates a simple mathematical concept. Is it a fairy tale, or a math lesson? I'd say it's both.
"The Animal Family books are not just written by their authors. They are studied and researched and lived into existence. Each book helps to make the world of nature that much more real, more understandable, and more valuable to children." ~Description from Stacey's website
This is a great starting telescope, and has a very comfortable-round shape. Astroscan Telescope is a high-performance telescope that is easy-to-use, maintenance-free and completely portable.
A long time ago, there was a great store in Noe Valley called "Star Magic". It had all kinds of cool stuff in it, most of it to do with space and science (but not all). That's where I bought an Astroscan telescope as a gift for my husband and eventually discovered Edmund Scientifics. Years later, GalaxyGoo became an Edmund Scientifics affiliate, and we're now linking to one of their products: the Astroscan telescope. Funny how life travels these little circles and spirals.
Up for a little time travel? Let's way go back to days of morse-code and the early "wireless". I haven't tried these kits yet, but they look very interesting: Radio Receiver and Morse Code Kit
The product description says that they're best for ages 10 and up. However, they also say, with adult supervision, they're good for ages 3 and up. Cool! Sounds like a family activity to me!

Puzzles! Brain Teasers! All in a little box! I try to keep things like this handy when traveling with the kids...or waiting for our order at a restaurant. Genius Decks

Shape Scapes Sculpture Set pieces have curvey shapes. Not your average construction set. While supposedly a kid's toy, it's also a nice desk toy.

Cool little stocking-stuffer: Staple-Less Stapler

These Robot Lamps are great! It's very cool that they've designed a version in "girly" colors too. It's sad that so many girls don't get to have robot toys, just because they don't come in pink. Well, now they can!

Kaleidoscopes are cool. Building your own is very cool.
Authentic Models Seeing Stars Kaleidoscope Kit kaleidoscope kit

Very handy for road trips, or any other time a kid (young or old) needs something distracting. It's all inside the travel box: gears, pens, paper. Nice and compact.
Curiosity Kits Travel Spin Doodles Travel Spin Doodles

These little markers are fantastic. Did I mention they're washable? Always a plus with art supplies for kids. They're also not as bulky as regular sized markers.
Crayola Pip-Squeaks Markers set of 16

The cool thing about these window mosaic kits is that you're not limited to the template they give you. You can reuse the tiles over and over again, creating your own designs.
Logic Links are great sequencing puzzles, and they come with colored chips to help visually organize thinking.

Math-terpieces, by Greg Tang, combines Art and Math in charming rhymes and puzzles. How could I not love it!? The puzzles are based around some of my favorite modern art pieces including April Showers (by Renoir) and The Starry Night (by van Gogh).
If you're looking gifts for a grade-shooler, you could get a few of Mr Tang's math-picture books. They're all fantastic!
This design is based on our click-n-spell with the elements game. Chocolate is spelled out with symbols from the periodic table of elements.

A GalaxyGoo original...The Cell! A great t-shirt for any Biology or Science Geek. The design is inspired by The Cell Project at GalaxyGoo.