Morocco doesn't have a huge road network, so a single country-wide map with a scale of 1:1,000,000 is sufficient. This will show most unsurfaced roads suitable for 4WD traffic. With a map of 1:1,000,000 it's easy to get suckered into days that involve huge distances, so it's as well to have an equivalent scale map of the UK to give you an appreciation for what you are planning.
Michelin 742 is probably the best all-round map as it shows scenic routes (in green) and those roads that might be closed due to winter snow (blue). A new version of the UK edition was released in May 2007 but there are only a few differences from the old version.
The IGN map is useful as it has gridlines to enable GPS waypoints to be roughly calculated. The Rough Guide map is also good as it's printed on a plastic-like surface that is more practical for tank bags.
There are larger-scale maps available but these are extremely out-of-date and, given the rate of road sealing going on in Morocco, are practically useless for ascertaining road conditions. Stanfords is an excellent mail order resource for maps of Morocco.
GARMIN GPS NAVIGATION
The coverage of Morocco included in the Atlantic basemap loaded in Garmin Streetpilot/Quest units is actually more detailed and extends further south than the coverage shown in Mapsource. Compare them side-by-side to see.
The best solution is the free-of-charge Marokko Topo maps at http://www.island-olaf.de/travel/marokko/gps.html I have travelled extensively with these maps and found the roads and tracks are accurate. The most recent version is December 2007. For best results on the road only download the street maps to the GPS unit (i.e. remove the topo overlay from the download) as otherwise you can get confused between contour lines and tracks.
The Marokko Topo map segments don't take up much storage space as they don't include routing information. Consequently, when you come to plan a route using roads, you'll find the GPS will only use the original basemap roads. Which leads to the second point, that GPS navigation in Morocco is best done as 'off-road' straight lines between known waypoints.
Don't bother buying tracklogs of Moroccan pistes, the vast majority of the pistes are already on Maroc Topo.
When planning Ceuta to Fes, be aware that Issaguen (called Ketama on some maps) in the Rif Mountains is the centre of the cannabis trade, and it's advised that you don't stop for people waving you down. I used to recommend avoiding the area but it has great biking roads and the situation is much better since the King's visit in 2012.
Gandini's series of six books on Moroccan pistes is the best resource for piste information. The High/Middle Atlas edition was updated in 2006. Written in French but not too difficult to understand
Voyages 4x4 is a french website with a variety of suggested pistes and waypoints.
Chris Scott's Sahara Overland 2 is another acknowledged resource for advice and information about pistes throughout the Sahara area and includes 12 pistes for Morocco.
Edit: Chris is currently working on a new book, Morocco Overland, with 40 detailed tracks for Morocco which is due to be published early 2009.
If you have a recent version of Mapsource you can check the validity of waypointed routes by parsing them through Google Earth. To see what this looks like (needs Google Earth but not Mapsource), click here to download (save, then unzip) Chris Scott's M6 route in .kmz Google Earth format. You can zoom in on the route and in some cases follow it on the ground.
Morocco has been described as a 'cold country with a hot sun' and temperatures can vary suprisingly. The all-time coldest temperature recorded in Morocco was -24°C (-11°F) at Ifrane in the Middle Atlas. On the other hand it regularly soars to 50°C in the area around Figuig. Summer night temperatures can be awfully sticky in non-mountainous regions.
In 2006 Morocco has received large amounts of rainfall and the effects in terms of plant growth and water table height are likely to last a couple of years. In June very heavy rains in east and south-east Morocco (from the Mediterranean coast to the Tafilalt region) killed 6 people. Merzouga (in what is regarded as a semi-desert region) had 105 mm of water (over 4 inches) in 2 hours, and the Hassan Addakhil reservoir received 39 million cubic meters. 2008 has been another wet year and some of the more remote tracks may not be in particularly good repair.
As of April 2009 leaded fuel has practically disappeared in Morocco and all fuel stations serve super unleaded and Eurodiesel 50. Afriquia is the best chain of petrol stations in Morocco with modern services and normally with an onsite cafe. Other chains are Total, Ziz and CHM. Petrol costs about 10.5dh/litre which is about 75p/litre.
Getting small change is often a problem in Morocco, so I often fill up asking for 120dh at a time (cent vingt dirham, SVP), this way I get change of a 50 and a 20 dh notes plus a 10dh coin.
Until recently it was practically impossible to get unleaded petrol south of Tan Tan. This may well have changed but I don't have any reliable information. Fuel prices in Western Sahara are roughly half of those elsewhere in Morocco.
'Loco for Motos' points out that Marjane Hypermarkets in major cities will take credit cards, however this can add ten minutes on to your stop. Marjane is also a good place to stock up on European items, wine and beer.
Mobile phone coverage
Morocco has jumped a technology generation and the market penetration of mobile phones is something like eight times than of landlines. This market penetration could only be achieved by the phone companies installing cellphone masts along all the normal traffic routes, whether tarmac or piste. Consequently you can be in really remote areas which in the UK would be signal-less and get all the bars on your phone. Make sure you have roaming enabled on your UK phone before leaving.
Jan 08: Vodafone and Orange don't have roaming agreements with suppliers in Western Sahara and Mauritania but O2 is said to be OK.
To make the best of the Moroccan coverage (and overcome the problem above), take a spare mobile with you to Morocco and buy a local SIM card (~£2). If the mobile isn't unlocked there will be someone who will do that for you. Now top the card up and use it to keep in touch with your fellow travellers, make hotel bookings ahead, and so forth.