Windows keyboard prepared with Microsoft's Keyboard Layout Creator.

Mac OS X 10.5
Download from here. Run the package to install the keyboard layouts and use the 'System Preferences' -> 'International' -> 'Input Menu' tab to select the Hausa keyboard. Switch to Hausa to use it. You may use the 'Keyboard Viewer' to view the key placements or simply view the slideshow attached to this post.

Mac OSX keyboard prepared with SIL's Ukelele.

Ubuntu
Available on Ubuntu since Ubuntu 6.06. Install as normal.