What kind of boards do you use for a stacked cake and what do you cover them with?

Just use the regular cake boards..either cut to size or the ones that are already the size you need. A really good idea is to cover them in plastic wrap, but I prefer press n seal. You need to cover the bottom of the board, too.

i use foam core and cover with contact paper, usually white if its going inside the cake

It depends on how big and heavy they are. I sometimes glue atwo together for more supurt, or use foamcore, or if they are realy heavy, my cake store has wood ones...

As far as covering, I have used all kids of things, foil, wrapping papper, scrapbook paper, fondant....

Good Luck!