I found a couple really nice old cabinets at the fleamarket that work great for displaying my mugs. This not only looks nice, but it gets them out of the Root Beer room and into the main room, which gave me a lot more room for other items in the root beer room. :-)
Here are some of my more recent additions.
I realize these are glasses and not mugs, but I wanted to fit them in here somewhere.
As I travel around I find some local drive-ins that had their own mugs. A good example is the first one below, Jerry's Beefburgers