This is a modification of Brian Hockenmaier's "8-bit Videogame Coasters" rack for eight coasters.
http://www.thingiverse.com/thing:115150

People in our makerspace kept breaking the corners off the rack, so I simply extended the edges of each corner to make them more resistant to those sorts of shenanigans.

Thank you to Brian for an absolutely awesome design! We get compliments on them nearly every day.