What is the perferred material for a TT shelf?

I went to my local acrylic workshop in an industrial area and had them custom make mine. It consists of two 1" slabs of clear acrylic. The top one has a channel routed out to the shape of an acrylic cover I had made so when it sits on top, it can't slide around. I used isolation dots from herbie's audio lab under the base layer and between the two slabs.  The look is beautiful and the functionality great. You can see it on my virtual system page.

wood

Depends on the type of suspension you have.  If it is the now typical solid (or mildly isolated) suspension then hard maple butcher block makes an excellent base.  Other woods may work too, but hard maple is the most recommended.  Using harder materials like stone, glass, or maybe acrylic provides less damping and can negatively impact the sound.  There are of course folks who will insist the harder materials work fine, but you takes your chances....  Now if your turntable has a spring suspension you may have more choices, the springs help isolate the table from the shelf material, though I would still suggest maple. 

sorry for the misspelling. If I go solid wood, does it really matter what wood: maple, cherry or walnut?