I can't seem to recall how many times I have been asked by folks about the availability of CAD software for Windows Mobile devices. Well, word came to me of Shape, a CAD application for Windows Mobile devices from OMNI DATA. Shape provides the ability to create CAD drawings on a Windows Mobile device, as well as the ability to export the drawings in DXF format, making the result highly compatible with desktop CAD packages.
You can check out more information (including lots of screenshots) at the Shape home page. The web site lists Shape at $99 USD, but a trial version is available (the trial version is fully functional expect for export abilities).