Shawn Medero posted a really good article about paper prototyping.
As interfaces become ever more complex and development schedules seem to get shorter and shorter, you may find it useful to give up your user-interface modeling software for awhile in favor of something simpler. All you need is paper, pens, scissors, and your imagination.
Since we started with prototyping for Pagebakery our selves this week, this is a perfect help at hand and surely will help us alot the next days.
He also posted a link to PaperPrototyping.com, which is also new for me, good stuff!