What to place under speaker spikes on hardwood

Sound Anchors has a nice product -- check it out at their website.
I wouldn't use the Target discs, if they're the same ones that came with my Target amp stand. I now have four small donut shaped dark marks on my wood floor that won't come off.
I'm using some brass discs slightly smaller than the size of a quarter with a depression in the middle of each for the spike. I think they were being sold at one time by Goldmund for about $4. each, but I couldn't tell you where else to find them.

Cut 2 3/4" MDF platforms aquired from the near-by Home Depot so that it's surface area is approximately >=1.5x larger than the cabinete base.
Place this platform on the vibrapods(get 4 per each platform at least) of sufficient quantity and grade. Place your speakers onto these platforms. The whole tweak'n'convenience is just arround $50.

Linn makes "skeets" that are designed for this. Thet are heavy round discs with holes in the center for the spikes. (I do not know what they are made of, but they are somewhat heavy for their size.)

I use them and have no trouble sliding my speakers w/o scratching the floor.

I have went the "pennies" route, what a nightmare! Do it right and save yourself a headache!!!

Coins. Of suitably high denomination to reflect the cost
of the speakers ;-)

John.

Linn Skeets, they are just what you are looking for. ~ $75 for a box of eight.