Some of the ideas are entertaining methods to demonstrate inertia and other physics principles to your dining companion. For example, you can hold the bottle by its end and swing it around in a circle as fast as you can, letting the centripetal force push the contents toward the cap. 

If you lack a basic fear of sharp objects, you could also attempt this Instructable for getting that last load out of a bottle of laundry detergent, or this suggestion from a Consumerist reader. Of course, you could perhaps more easily just rinse the bottle out with some of the laundry water, or even let gravity do its thing by standing the bottle upside down so it gradually drains into the cap.

What about dish detergent? When a bottle is nearly empty, you can fill it with water and use that sudsy water to clean things.  

And those little slivers of bar soap? There are a bunch of options. Wet a new bar of soap and try to glue it to the old one. Or you could cut a hole in a sponge, insert the sliver and use it in the bath. Try the same thing with a bath mitt, if you've got one handy.

Or you could save a bunch of slivers to make your own body wash or liquid hand soap. Just put the soap slivers in a heat-proof container (a glass jar could work, or an old pot)and slowly add boiling water while stirring until it reaches the right consistency.

Now, full disclosure: any savings gleaned from these tips is likely to be small --- on the order of cents, not dollars --- but so is the expenditure of energy needed to employ these techniques. The virtuous feeling of reducing waste, however, is priceless.

(photo: stock.xchng)