The hill of the Hotel Atlas is a good viewpoint on the town and the valley, especially on sunsets. It can be reached from the south gate of the medina Bab el-Ain by climbing the road coasting the medina on the west side until the east gate Bab Souk, and then uphill, crossing the old cemetery on a rocky path.
The medina maps: (http://www.chaouen.info/assets/mapachaouen.jpg (http://www.planetware.com...) is the focal point of interest for most visitors to Chefchaouen. Walking around the town with its whitewashed walls, originally decorated in this style by Jewish immigrants, can be a nice change to the hustle and bustle of the cities of Marrakech, Rabat, and Fez.
The waterfall Ras el Maa to the east of the medina is a meeting point for local residents who come to cool off, chat and do their laundry including carpets on sunny sundays. The café nearby is rather expensive, however it's a nice change from the main square.
The ruins of an old mosque Jemaa Bouzafar, on a hill behind the waterfall, overlook the medina and its crumbling tower offers great views of the town.
Kasbah
Looks quite interesting from the outside, but there isn't much to see inside. The place is well preserved. There's the tower and the prison amongst others that's worth a visit, and the courtyard is green and almost alien amdist the mountain setting. Should only be an option if you're either bored or want to get away from the bustle outside.