Ive made a few homemade bongs so im gonna try to help you out. Im assuming you want to use items from around your house, but your best bet would be go to a hardware store and look around. Be creative.

You can make a bong how Leary said, but if you have the concept of how a bong works then you can make a different, maybe more reliable bong. Use your noodle.
I mean your head. The head on your shoulders. Damn, you get it.

Socket heads work great as bowls. And look for tubing or something you can use for a stem.

If you have a gluegun, your bong will last much longer.

Good luck, and youll think of something.