The taiko musubi ("drum knot") is the most used musubi these days. It is simple and subdued and resembles a box. The taiko musubi is suited for both old and young women in almost any occasion and goes with almost any kind of kimono and in some cases even with yukata. Only furisode are considered too formal and youthful to be worn with the taiko musubi.
The writing on the obi is "Setsugekka": snow, moon and flower. More information about this can be found here.