ManDrake is a man page editor for Mac OS X. ManDrake uses a side-by-side display that shows the troff macro source in one pane and the formatted man page in the other. The formatted view automatically updates as you edit the source.
If you're new to writing man pages, I recommend that you check out Practical UNIX Manuals: mdoc for a good overview of man page style and form and MDOC(7) for a good reference on the available formatting macros.
This project is a fork of the original by Sveinbjörn Þórðarson. Many thanks to Sveinbjörn for this wonderful app -- it has saved me countless hours of frustration and made creating man pages tolerable, if not exactly fun. Sveinbjörn's ManDrake project page is located at http://sveinbjorn.org/mandrake. ManDrake is distributed under the GNU General Public License v2.