like this for $4. It is SUCH a fun toy (for kids and adults) and the possibilities are endless. My son's review was "This is one of the awesomest toys of my life!" Marbulous is available for purchase at various places, but you can also try your hand at making your own marble run. See this one from Mrs. Myers' Kindergarten blog.
Skill sticks (as they're called) are available at Amazon, JoAnn, etc.
#6 - Make Your Own Lemonade Stand Computer Game - Using a simple computer game, the kids become their own lemonade stand owners, deciding how much lemonade to make and how much to charge, taking into account simple variables such as the weather and cost of lemonade. It really held our son's attention, and he wanted to play all three levels of the game. Here's the exact game we played in the museum (for free)!
Moneyville Lemonade Stand Game
The thing I really loved about these six concepts is that they're simple - Using blocks, marbles, bikes, and crafts, you can still create an environment that holds kids' attention. What are your low-tech favorites?