If you think that science can only be done using expensive materials and equipment then you should take a look at How to Fossilise Your Hamster: And Other Amazing Experiments For The Armchair Scientist
. Mick O'Hare
will give you plenty of ideas for experiments which you can do using everyday things.
For instance you can extract your own DNA , and can find the iron in some breakfast cereals.. You can show that hot water really does freeze faster than cold water, and your can make plastic from milk and vinegar. At first I wondered why a book that seemed to be aimed at children was a contender in the adult list for the Royal Society Prizes for Science Books. But clearly many of the experiments need adult supervision, and the book starts off with several experiments involving alcoholic drinks, so this categorization became understandable. Some of the experiments were more along the lines of explaining the science behind everyday objects such as paper planes and yo-yo's which I felt didn't fit so well into this format. I don;t think that anyone would really want to fossilise their hamster either. But there are plenty that clearly gave the New Scientist team a lot of fun. I think that this is probably the best way to do these experiments - in a group, maybe as an activity to do with your children. And even if you don't do any of them the book still provides something amusing to read at odd moments