I think we should have some bonding time. Chemical bonding, that is. In the clever chemical puzzler Sokobond, you're given a handful of atoms and the task of them joining them all by pushing and chaining them together. Like Sokoban puzzles you might be familiar with, you don't have much space to do it all in, so you've got to use the splitters, bonders, and rotators provided. Even if you don't give a hoot for chemistry, Sokobond is still a very accessible puzzle with easy-to-learn rules and an enjoyably element-ary design.
Wanna see a crazy experiment in game design? Experiment 12 is a collaborative game created by twelve developers, with each level building on the story set by the previous ones. You wake up in a testing chamber, but it's hard to tell where you'll be headed from there, as each level chapter introduces a new puzzle or platform element for you to tackle.
BRICK[bricksmash]SMASH is a bunch of tiny Breakout clones within a Breakout clone: each time your ball hits a brick, it spawns a tiny ball inside the brick it hits. Once each brick runs out of tiny bricks, it disappears and the balls inside the brick are set free. Don't try this with real bricks or you'll end up warping reality. (Try it on the computer instead, and you make a rainbow!)
Interactive art has a reputation for being light on the challenge, but These Robotic Hearts of Mine, a puzzle game by Alan Hazelden definitely shows that it doesn't have to be. It's a simple game of gears and direction... one that I would love to see re-created in the physical space of a gallery. However, each solution presents another line in a story of technology, hearts and heartbreak. The puzzles alone would be fine, and the elegy is affecting. However, the combination fits like one hand into another.