Saturday, we were at a friends house with my portable kegerator:
As you can see, it doesn't yet have a drip tray.
My friend came out with a folded tablecloth, which he placed in the "drip area". Instant "drip rag", no tray needed!
Now, I am thinking of getting "fancy" with the idea. Do they make the thin "kitchen sponge" material in large sheets? That could be cut into sections that would work great at catching drips and spills. It could have a secondary function of acting as a sponge to clean up the kegerator after a party.