I guessed the right choice after posting a brainstorming methodology was to give low quality wireframing ideas. Personally, I like to use Balsamiq Mockups. It is easy to use and it gets the job done pretty nicely.
I did an example on my blog as a demonstration:
What is your favorite option? I’ve used Axure too, but for low quality I find it to be a bit too much. Still, if you want something high quality, Axure is a good option.
If you want more sketching options, here’s an article I found not so long ago on the subject. I don’t think it gets any better than that.