Question for DIY people: Butcher block shelving??

I picked up the "Spar" maple butcher block from IKEA the other day. (Link to the butcher block is here) => http://www.ikea.com/webapp/wcs/stores/servlet/ProductDisplay?catalogId=10101&storeId=12&langId=-1&productId=15241

I am going to use these blocks to replace the cheap MDF shelves on my welded steel Target rack. I believe the blocks are unfinished. They are not solid chunks of maple -- there is some hollowness inside.

My question is, what should I do with them next to increase their effectiveness as shelves and to increase their durability? Should I oil them? Put a coat of lacquer on them? Glue cork and/or rubber to the underside?

I will be placing them under a variety of components (Cd player, amp, power conditioner), so I could customize each block to suit the component it sits on.

Any suggestions would be appreciated!!!! Thanks!!!!