What to place under speaker spikes on hardwood

Target (and other companies) make a product just for this
purpose...unfortunately I don't remember what they're called. They cost $30 for a set of four. They don't slide
around, however.

I found "footers" for sale at Audio Advisor which are designed to hold the point of the spike and protect hardwood floors. They came with an adhesive on the bottom covered by thin paper, which will come off if you try to slide heavy equipment, the result being they will stick to the floor. This may be sonically better, but inconvenient. I bought some teflon furniture sliders at Home Depot in the appropriate size, which also have an adhesive side, and stuck them to the bottom of the footers. I have them under my speakers (ML SL-3) and equipment rack, and have not noticed any significant deterioration (or improvement, for that matter) in the sound as compared to the footers without the teflon, but they slide quite satisfactorily. If I glued them to the floor, it might sound better, but I have not been willing to do that.

You could purchase audio point disks, however they will not allow the speakers to slide without scratching up your hard wood floor. If the product allowes you to slide the speakers around it will defeat the sonic feature/purpose of the speaker spike.

Nickels for silver spikes or pennies for brass ones!
Don't worry about dulling the points. The force per square inch is still ridiculously high, so the coupling will work.
The teflon sliders MAY work, but I fear they'd wiggle in the low bass, like sorbo-pucks, etc.
Have fun.

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.