OmniGraffle 


OmniGraffle is the closest thing to Visio on Mac OS X, and raises the bar in terms of what a drawing application should work like (its polished UI and helper guides remind me a bit of Aslhar Vellum, which I used many years ago):

Resources:

Notes:

  • Version 5 was released on Mar 6, 2008, with improved Visio support.