Fantastic Contraptions - Will drive you MAD!!!

[AtomFun]

Click the link and enjoy.

http://fantasticcontraption.com/

Post back and let us know what level you get to and how many wasted hours getting there 

[Richard Marler]

already done it. completed. too many hours. makes you laugh a lot.

[Drinks]

Likewise already done it, it took a while but it's great fun.

Also worth a look is http://www.miniclip.com/games/magic-pen/en/
Not quite as good as you can't make machines but still entertaining.

[ross]

If you like that , try 'Phun':-

http://www.phunland.com/wiki/Home

Very cool as you can have liquids in your models.