One great way to do this is by distinguishing her bridesmaid's dress. We like the idea of having all the bridesmaid dresses be the same color, but maybe have the Maid of Honor's be a different fabric.
If the rest of the bridesmaids dresses are chiffon, pick a more formal silk or satin for the Maid of Honor's and so on. A special friend deserves a special touch, and if you don't like the idea of different fabrics, maybe a pretty fashion tote or a gorgeous clutch is the key.
Any way you choose, make sure you give your Maid of Honor the props she deserves for being awesome!