Hausa is an official language in northern Nigeria and widely used in other Muslim areas of West Africa as well. The standard Latin orthography uses the normal English alphabet, plus the hooked letters Ɓ ɓ Ɗ ɗ Ƙ ƙ Ƴ ƴ. Of the fonts included with OS X, only Lucida Grande has these, but others can be downloaded. In addition, some publications have used a dot underneath instead of the hooked letters, and some dictionaries and teaching aids may also mark vowel length using a macron ¯ and vowel tones using grave ` (low), acute ´ (high), and circumflex ˆ (falling).
All of these can be made using the US Extended keyboard layout, a chart for which is here. The hooked letters are made using Option + Shift + . (period), followed by the base letter. Another solution is to use the custom Hausa keyboard layout from my iDisk. The hooked letters are located on the Option version of the base letter.
Hausa has also been written in Arabic script, and examples of that can be found on Nigerian banknotes.