OmniGraffle Stenciltown
Stenciltown makes it easy to find free OmniGraffle stencils which have been shared by the community. You can browse and search the collection through its web interface, and once you’ve found a stencil you’d like to use it’s as easy as ever to download and use.
You can also search Stenciltown from within OmniGraffle itself, both on Mac and iPad.