Storyboard That is a cutting edge Web 2.0 tool for rapidly creating amazing storyboards, no art skills needed. Great for business meetings and in the classroom for students to express their creativity.
LL Note: If you want to print out the free version storyboard, it puts a big digital watermark across your pictures. I found a work-around for that: take a screen shot, then edit that picture as you need to. Short term, for small projects, it's workable. If I were going to use this on a regular basis, I'd ask my school to get us a subscription.
It calls itself a storyboard program, but it really works much more like a comic strip. But it could be very useful for brainstorming in class. You can make 3 free storyboards a week, which might be enough for many of us. It's really easy to use, and you can customize some of the features with your choice of color.