What's under your bookshelf speakers?

I recently picked up a pair of ProAc Tablette Reference 8 Signatures in bird's eye maple for my office system. I would like to protect the finish on the bottom, but also preserve/enhance the sonics. At the same time, seeing as how this is in my office, I would like to keep things visually discrete. Currently, I have a small mouse pad underneath each one, and in truth, this seems like it might be a viable option. However, I haven't tried them with another product underneath them or with nothing underneath (don't want to damage the finish), so I am not sure what sonic effects the mouse pads are having. The system sounds pretty good as is, though.

Thanks, Tom.
I use sorbothane pads, available from an Audiogon member here. I haven't compared them directly to any other isolation device but, if it's isolation you're interested in, sorbothane is the usual prescription for an inexpensive solution and these are visually very unobtrusive.
If you don't want to damage the finish of the speakers or your desk, be careful about sorbothane - it can damage speaker and furniture finishs unless you put something between the sorbothane materiel and the finish. If you can stand the appearance, your mouse pads could work quite well for these small speakers. I wouldn't get too anal about this....small felt pads would probably do as well.
Thanks for the heads up. Damaging the finish is the last thing that I want to do. In truth, the mouse pads don't look too bad. They are only slightly larger than the speakers, and I could always trim them down to size.

I use the stuff that is used to keep area rugs from sliding around. It's available in various sizes at home centers or discount stores. It's only 1/16" thick and can be cut easily with scissors.
A very similar product to what Mijknarf suggests is a rubberized shelf/drawer liner that you can buy anywhere - Walmart for instance. Comes in a few different colors (not that you'll see it under the speakers) and in much smaller sizes than the product for area rugs.
I'm glad I asked this question! These are some very innovative ideas!

Thanks, Tom.
Like spikes on large floor standing speakers, the idea is to decouple the speakers from floor or stands. So any "soft" materials will have absorbing effect and slightly smear the mid and bass definition, if you can hear it.

Hard material is better, but they will scratch the nice finish of speakers. I will recommend BDR cones which has rounded tip and will not damage the surface. Problem is they are slippery and speakers can "fall off" from the cones. That has happened to mine, cost a lot more to repair the speakers when damage is on top than some minor dents or scratches on the bottom of speakers.
I'm using cork, cut to fit the top of the speaker stand. Good grip and doesn't cause marking or damage to the speaker bottom.
I would recommend Blu-Tak as well if you are using speaker stands. Works like glue but does not leave any marks. Also since this is not really damping material, there should be no smearing of the Mid and Bass definition. And spikes are probably good for the stands...
Blu-Tak *will* leave stains after long periods of time on some surfaces. I'm impressed by Wrayman's cork idea, that sounds to me like the best yet - I'm glad I stopped by!
Mapleshade records recommends spikes to de couple the speaker from the stand. As a last resource use wood plugs which are better than any soft material. Best thing about all these suggestions is that they are not costly.
I can also vouch for cork...which can be found in smaller "panels"...and which has a harder density fiber board on the back...these were often used to assembly cork wallpaper...which I had as a kid...and is much more durable,affordable, etc. than thicker slabs of pure cork(the cork is actually only on one side)...and to my ears doesnt "deaden" the sound as much...good luck...
If damaging the finish on your speakers is an issue, be careful with the Isoblocks. I've used a set in the past and, while they do provide good isolation, the black rubber left unremovable marks on both the bottoms of the speakers and a hardwood floor.

With any soft compound like the Isoblocks or the sorbothane pads I recommended above, you'll need to put something between the pads and the speaker. Saran Wrap works, or any thin plastic like that.
Thanks for the tip. I've had problems with vibrapods but didn't anticipate it with the isoblocks.
Just an update, I ended up going with the sorbothane pads from Zonus (with plastic between them and the bottom of the speakers), and I am pleased with the results. Definition and soundstage seemed to have improved, despite a less than idea positioning situation. On a somewhat related note, my speakers are located near my big old IBM Netfinity 5000 series server (which I turn off, if I ever get in the mood for more intense listening), and it generates a good deal of vibration. So, I picked up four extra sorbothane pads, and viola! No vibration from the server can be felt at all even with your hand right next to it (the server is sitting atop the desk one of the speakers is on), and it also made the fan noise much quieter.

Thanks again for all the help.