I recently found a bunch of mat 'centers' that were cut out of some 8x10 mats that I used to float some small 3x5 paintings in. Since I can't stand thowing anything away that might have some use, I decided to see how one would take watercolor. Worked pretty well, and I really like the beveled edges!
My real thought behind this trial was the possibility of taking several along on my next road trip, and I'm trying different media to see which might be the least cumbersome to handle on my lap in a vehicle (as a passenger, of course! ;) I may try colored pencil next, although I like the speed and fluidity of the watercolor.