World village

The official website of Mauritania
http://www.mauritania.mr/

A good general map (full size) edited by the French publisher Le Routard.
http://www.routard.com/images_contenu/partir/destination/mauritanie/carte/mauritaniepop.gif

Some general information given by the always excellent wikipaedia and wikitravel
http://en.wikipedia.org/wiki/Mauritania/
http://wikitravel.org/en/Mauritania

The Lonely Planet pages on Mauritania
http://www.lonelyplanet.com/worldguide/destinations/africa/mauritania/

You can discover the 6 languages spokent in Mauritania on the "Ethnologue" website.
http://www.ethnologue.com/show_country.asp?name=Mauritania