I have provided three OmniGraffle templates on the Graffletopia website to help users design web forms effectively.  The templates are based on research by Matteo Penzo with design guidance from Luke Wroblewski.  Two of the templates are free whilst the third can be purchased.  At the time of writing the templates have been downloaded over 80,000 times.

Images can be clicked below to be taken to the download page on the Graffletopia website.