Great resource.

Discovered the site several years and helped in creating an offline version (only iOS) with all the content (as of 2012):

https://itunes.apple.com/us/app/toys-from-trash-arvind-gupta...

I particularly like:

CD spectrascope: http://arvindguptatoys.com/toys/cdspectroscope.html

Using polarised light to see stress in plastic: http://arvindguptatoys.com/toys/seestress.html

My favourite is the Homo Polar Motor:

http://www.arvindguptatoys.com/toys/homopolarmotor.html

So simple yet so magical.

Wow, this is really cool. I feel the quote on the front page is apt for a lot of us here at HN:

"And somewhere there are engineers helping others fly faster than sound. But, where are the engineers helping those who must live on the ground?"

We live in a world where return on capital and/or time invested is the common measure of success, but someone like this is having untold impact on many people's lives simply by applying their brilliant mind in a less commercially incentivised way.

These are great.

Always funny what these "make toys at home" folks think people have lying around their homes: http://arvindguptatoys.com/toys/Heartpuzzle.html

Wire is pretty common, sure you may not have any. I have plenty in my house, old coat hangers, wire for the garden, etc.

Wire and a set of pliers (to cut and twist the wire) is really useful stuff. Need to make a trellis for your plants? Chop a few twigs off a tree, tie together with a little wire. Need a little fence? Same deal. Maybe plastic zip-ties have made wire redundant?

It's not trash, though.