[michaelbuddy]

Axure is a good tool. Really easy to get up to speed and small niceties that keep things quickly moving. I like it better than the Free 'Pencil' software because you can mockup dropdowns really easy. You can also change the fidelity of the mockup so it looks like hand drawn. Seems gimmicky but people sometimes need it to be hammered into them that it's a wireframe.

When you export, you can export to a working clickable mockup with notes and things on it. I've felt pretty darn productive with Axure and that's why I recommend it.