From the airport, we took a train straight to Rabat. We left Casablanca for the end of the trip. I gave detailed tip on accommodation above. 

It's very easy to get around Morocco. The train network is good and orienting oneself is very simple. The same goes for the bus system. 

The main bus company in Morocco is CTM: http://www.ctm.ma/

The train company is ONCF: http://www.oncf.ma/Pages/Accueil.aspx

You can buy a first class or regular (second class) ticket. I found that the regular class seats are comfortable enough when you travel between cities. 

Some information about traveling times between the destinations:

• From Marrakech to Casablanca -- 3 hours
• From Marrakech to Rabat -- 4 hours
• From Marrakech to Fes -- 7 hours
• From Marrakech to Meknes -- 6 hours
• From Tangier to Marrakech -- 11 hours (direct overnight)
• From Tangier to Fes -- 5 hours
• From Casablanca to Fes -- 4 hours
• From Casablanca to Oujda -- 10 hours
• From the International Airport to Casablanca Center -- 40 mins

As for the prices:

• From Marrakech to Casablanca -- 140/90 Dirham
• From Marrakech to Rabat -- 185/120 Dirham
• From Marrakech to Fes -- 295/195 Dirham
• From Marrakech to Meknes -- 265/174 Dirham
• From Tangier to Marrakech -- 310/205 Dirham
• From Tangier to Fes -- 155/105 Dirham
• From Casablanca to Fes -- 165/110 Dirham
• From Casablanca to Oujda -- 305/205 Dirham
• From the International Airport to Casablanca Center -- 60/40 Dirham

Another link with more information about the trains:

http://goafrica.about.com/od/morocco/a/moroccotrain.htm

Plane ticket: After several days of inquiries and reading background material, I decided the best destination to land, in terms of cost, is Casablanca. I purchased an airline ticket through www.kayak.com with Turkish airlines for a 15 day trip.