Fun site of the day :)

Bridge Builder

If you're any kind of engineer (particularly mechanical/civil/structural), or liked Tinkertoys/Construx/Legos, or just like making bridges that will collapse when trains go over them, you'll like it. :)

Another fun site of the day

This one I've known about for a while, but had forgotten till I saw Bridge Builder--

Soda Constructor

Ths one lets you construct little shuffling, ambling, walking, squiggling creatures out of sticks and masses and springs.. fun to play around with :)