Hi all,
I realize there isn't much talk on this list about how to prototype with OmniGraffle, so for those of you who use it to make your wireframes and deliverables, you may find this post I wrote useful:
http://techblog.appnexus.com/2012/how-to-create-html-pdf-prototypes-using-omnigraffle-pro/
Feel free to comment (on the post is probably best) with any follow up questions.