I have had success with the ingredients mentioned below, and the procedure (in Norwegian) can be found at Nysgjerrigper.no (written by Hanne Finstad).
a sample of something living
detergent (soap of some sort, containing sodium lauryl sulphate)
There are plenty of good resources on this in english too, the research language above all. I have probably only seen a small percentage of them, but here are a few excellent sites:
How to extract DNA from anything living The University of Utah (with a funny twist)
DNA extraction The Gene School (good explanations)
How to extract DNA from fruits Fun Science Gallery (descriptive photos)