I always think Instructables like this are a little bit cheaty, i.e. take something that already goes bang and make it go bang in a different way. Point here I think is that if you take sensible precautions you can strip down and reuse stuff like this that would otherwise end up on the tip. Plus, we had a tonne more fun with the little firecrackers than we did when they were intact fireworks AND we got talking about all sorts of stuff like physics, combustion, sound waves and elasticity.
Full instructions here: http://baddadgreatkid.blogspot.co.uk/2012/08/homebrew-firecrackers.html
Bad Dad website: http://baddadgreatkid.blogspot.co.uk
PS I'm the chunky bloke running away a lot. Watch for my idiot moment at 2: 33.