OmniGraffle
I've seen OmniGraffle diagrams show up in a blog entry and and an article in the last week. Both diagrams show how OmniGraffle can produce high-quality, professional looking diagrams. The best part is that (I believe) it comes out-of-the-box with OS X. I seem to remember deleting it off my hard drive a while back b/c I didn't know what it was for. After seeing these sites, and realizing what OmniGraffle can do - I'll be searching through my Panther CDs in hopes of finding it. Anyone know where it's at and what version it is?