Skencil works with Mac OS X
I have been using skencil (sketch) on my iBook under Mac OS X since 2002 where it runs flawlessly in the X11 mode.
The simplest way of getting skencil installed is by using the Fink Commander.
As far as OS X comes shipped with Python it may also be installed just following the instructions for Unix/Linux. Find some additional hints for proper installation given for version 0.6.16 by W. Craig Carter with this screenshot and for 0.6.17 by Stewart Midwinter.
Screenshots:
The most prominent application of Skencil for me is preparing slides for presentations:
Most of the text in this slide is prepared with help of the TeXsketch plugin. It looks better in the PDF version presented by Acroread bottom left. In the OS X environment skencil coexists also with MS Office products (bottom right).


Alternate screenshot:
Here all text is native Skencil, though again it looks slightly better in the PDF.
The width and height of the slide are chosen to match standard dimensions of screen and LCD projector presentation. To make shure that the contents of the slide will appear on the PDF page centered in the same way as constructed by Skencil one has to fix the bounding box in the EPS file before epstopdf conversion:
%%BoundingBox: 0 0 720 540