Using the basic theory of electrolysis it is fairly simple to split the Hydrogen & Oxygen atoms from water. This project write-up gives a straight forward approach using household items to accomplish electrolysis. Be careful around pure hydrogen, remember the Hindenburg disaster!
PyroFactor: 
April 18th, 2008 at 5:03 pm
Don’t use table salt (sodium chloride) or you’ll end up with poisonous chlorine gas in your bubbles. Use some other kind of salt (e.g. Epsom salt) instead.