If you’ve downloaded Blend 3- or if you’ve heard a bit about it- you may have heard of the prototyping tool Sketchflow. It’s an extension of the Microsoft Expression Blend tool, and allows you to quickly design a site’s flow, page by page, and then define the components within it.
I started playing around with Sketchflow when I was tasked with coming up with a “grand master plan” for a project that I wanted to take on. Creating the page flow seemed easy enough; it wasn’t long before I had a nice little tree drawn that covered everything from the first page to the last, with neat little arrows directing the user’s flow. When you hit F5 (or build), you’re taken to a compiled version of the site, from which you can navigate to each of your pages. Pretty neat.
The real power came out when I started dropping in labels, textboxes, and buttons, and then attaching events from each of those buttons to navigate to other pages. Suddenly, I was able to take my prototype to the next level- instead of bits of scrap paper, I was creating an interactable demo that I could show off, that saved notes and annotations for later reviewal.  As soon as I had it figured out (mostly), I showed the other person that I was working with how to set up, and within a matter of minutes, we were designing away.
There’s a big difference when you can show off a “working” prototype instead of a few concept drawings; you could get a feel for the flow of the application, and because it felt more real, you could do a bit more of a gut-check. It felt closer to production, even though it really wasn’t any further than that scrap paper; and it took about as much time (in fact, probably less, edits are easier in digital format). And if you do feel inclined to shuffle around dead plants, you can always export the whole project as a Word doc.
P.S., one small hint- the “sketch” style is not on by default. It’s hidden under the controls chevron, if you click the triangle next to “Styles” and then “Sketchflow”. It is a HUGE PAIN to change styles… which kind of baffles me.