Speakers and stands: how to place?

Unless you have really high end stuff and are trying to max out resolution, etc, just use blue-tac or that stuff Gunbei recommended. The blue-tac is probably going to give your speakers a much more secure attachment to the stands (as opposed to spikes or cones) and will not really influence the sound of the speaker.

A great tweak I discovered five years ago is using artists kneaded erasers instead of blu-tack. One small pad can be sectioned into four pieces, then rolled into small grey booger-like balls and placed under each corner of the monitor. Kneaded erasers will hold the speakers to the stanbds like blu-tack but will clean completely off even after years of being in place. Wonderfully sticky and effective, clean up perfectly, and are cheap, cheap, cheap.

http://www.dickblick.com/zz215/02/

i have found that hard objects tend to enhance resolution, while softer objects, such as foam, and sorbethane tend to soften the sound.

there is another material, i believe it is called blu tack which when placed under a small speaker may reduce cabinet colorations, without creating the above mentioned effects. blu tack is a light sticky substance, reminds me of silly putty.

as to materials under the stand, hard objects are usually used, to treat problems in the bass. you may also want to weigh down the sands by adding sand or lead shot.