I personally did not have time for this, but I learned that the hotel can arrange for you to visit Mr. Cameroon for the day. It takes a couple of hours to get there, but worth it for a little trekkin!
A good afternoon's drive would be to the mountainside town of Buea via Limbe, about one and half hours from Douala's city center. Buea is perhaps the highest village on Mt. Cameroon, which also means it will probably be the first to go next time the volcano erupts.
Regardless, Buea is an old town with some German architectural influences that remain from the early colonial days when the Germans moved up the volcano to distance themselves from the French and English along the coast. Actually, the Germans probably settled at the higher elevation to escape the heat and humidity on the coast. As I ventured up the mountain, I could feel the temperature begin to cool and by the time we reached Buea it felt at least ten degrees cooler than in Douala.
Unfortunately for me, the day I went to Buea there was a heavy cloud cover, so, the summit of Mt. Cameroon was not visible. Naturally, this didn't stop Rolf and I from eating a few chickens and drinking some "33" at one of the locals while enjoying what view we did have...
So, minus the view of the summit, the drive was made worth it by the simple fact that you pass through so many shantytowns with roadside markets. Kids were selling fresh bush meat and vegetables at the side of the road, people washing their cars (or kids) in the streams flowing down the side of the volcano and those who were just sipping "33" in the roadside cafes were all interesting to watch.