Ultra-quick mockup, using Balsamiq
Just tried out the web demo of a wireframing tool that a coworker had mentioned, Balsamiq Mockups. I was very impressed. I was able to jump in and start dragging and typing, and finish my initial layout in about 2 minutes. Then I tweaked, re-arranged, added, and removed elements with absolute ease. Not once did I have to pause and think about where a particular function might be located, or have to fight against awkward dragging or resizing behavior.