In reply to JCLeeds:
The only place i've heard of near Marrakesh is Todra Gorge
http://www.ukclimbing.com/articles/page.php?id=766 Ukc did a destination article. But it's says it's 5-8 hours from Marrakesh...so probably not worth it for a single day. If you could do 2 days or more, might be worth the trip.
The rest of the developed climbing afaik is in the anti-atlas mountains and is definite trip in it's self (i'd totally recommend it!) but literally nothing for non-climbers or even rest days