I posted this in another thread:
Do you have an empty CO2 cartridge for a BB gun? If so, an easy way to make the bowlpeice for the bong is to cut off the end of the cartridge with a hacksaw. To do this, clamp the cartridge down in a vice and cut where the end of the cartridge starts to taper down. You will come out with a NICE bowl peice. This is probably the most important part of the bong.
If you need to make a hose, but can't think of anything to use, get an extention cord and cut off a segment that is as long as you want the hose. The, with pliers, start pulling the wires out of the extention cord. Then clamp the wires down in a vice and start working the rubber off of the extention cord. You will come out with a nice ass hose.