What does everyone use to cover there cake boards? What does everyone use as there cake boards? What is the cheapest, best looking, easiest thing to use?

sorry to be a pain, but it's "their", not "there" cakeboards, that's one of my major pet peeves LOL.
I use either the silver or gold cake boards if it's a one tier cake, or foil covered cake drums (white, gold or silver), both of which are available online

For fondant covered cakes I use a fondant covered cake board. I use 3 cardboard circles a few inches larger than the cake, "glued" together, then covered with fondant to match cake, fabric ribbon around the border.
For buttercream (or other non-fondant cakes) I use a gold board. They are fairly inexpensive (about $1, depending on size) at my local cake supply shop.

Either way, I figure the cake board costs me about $1-$2.

I use foamcore. I usually have to get it at my local Wal-mart because there are no cake or hobby supply stores within 50 miles. I double or triple them for one cake board, depending on the size of the cake. They cost about about 2.75 per board (poster size) but I can get several cake circles out of one.

I have several mirrors that I use for fancier cakes. Just charge a deposit enough to cover it if it needs replacing.

I use 1/2" plywood boards. My clients ALWAYS return my boards!