The Color Splash Camera looks like a lot of fun. Retro and techy, at the same time.

Gift certificates are great! Especially as gifts for kids' teachers!
Science & Tech:
Edmund Scientifics Gift Certificates
For the kitchen:
Sur La Table Gift Certificates
The Perfect Gift - A CHEFS Catalog Gift Card
Family:
Leaps & Bounds Gift Certificates
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

I haven't tried this kit, but it looks pretty straightforward and easy to build...with styrofoam balls as phospate groups and sugars.
FloraCraft Fun Learning DNA Kit DNA model kit

3D Digi-Draw looks like a really fun toy! I've always found drawing to be a challenge, and something like this might have been helpful when I was a kid. The product description says it can be used for 3-d objects, but I wonder what it does with perspective. I might get one just to try it out myself :-)
Mechanically, it looks nice and simple, with no batteries or power requirements. Nice!
I't's more color theory than chemistry, but it's a great bath toy!
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.