While I've discovered WIFI in Nouakachotte, thought it may be useful to share a few Mauritania tips.
Writiing as desert viirgin, first time desert driving experience (Toyota landcruiser, Barry and I on 3 month drive from UK to Mauri, Mali, BF, Togo Chad etc.)

- You gotta have EURO's in Mauri.
To our horror, banks will not change, have not heard of the Pound, Livre Stirling, L'argent Anglaism, whatever its name, it is not LIKED or wanted. Here in capital Nouakchotte, no bank will accept but direct to black market.
We can mostly only get the same as the exhaulted EURO.
Even the old faithful dollar is not wanted or liked. Here the EURO is KING.
Good idea to get a print out of the base rate from a bank, and use this as the basis for negotiation.

- We were advised that gasoil/petrol and food were expensive in Mauri, so we stocked up in Morocco with both. Good idea, and true. However at the boarder the customs officer most unhappy with all of us coming over will full jerry cans. 'We have petrol here in Mauritania' he said, demanding we left our jerries behind. We got away with not leaving them in the end.
They also searched the car for alcohol.

- Best first experience, driving over pieste Nouadibou to Chom, following the Train de Desert. camping out, loving each day and each night. Got stuck in sand, got punctures, got experience!

- Gasoil /Petrol ok to buy at Chom, from the school teacher at the end of the street.

- For sheer enjoymnent of not restrictions of health and safety to the wind, and great landforms highly recommend the AMOJAR pass - as Chris recommends from Chingetti to Atta. What a great unfolding.

- For sand driving, the drive from Chingetti to Ouadane.
(good camping)

- Get a Mauritanian mobile, very easy and not expensive.

- Every office closes on a friday to Sunday, opening Monday to Thursday.
We keep missing working days to get our visa's!
Although you are given a 15 day visa at Mauri frontier, i gather you can ask for longer ie 20 or 30.

Heading off towards Mali boarder, via the crocodiles, and more sand.

Rachel and Barry