For that sort of thing, I use a whole variety of tools, a lot of Adobe just because it's convenient. Note that I use a tablet instead a mouse, which also makes a difference.
For pure wireframing and basic storyboarding I usually go with something like Illustrator (with the Interactive Sketching Notation symbol set:
http://www.linowski.ca/sketching); Fireworks / Photoshop on occasion
For prototyping, Axure (
http://www.axure.com/) is nice, and I've also used Balsamiq. Omnigraffle is very good as well, although since we use mostly Windows machines, I tend to use cross-platform options more often than not.