I tend to use a notebook for each novel that has random notes I want to keep track of. I start my novel with my concept and my character and work from there. But I like the idea of brainstorming beforehand. So I will give that MindMeister a go.
I also have been using Workflowy for my extensive novel notes which is mentioned for outlining. It is a great little online program you can use to categorize your thoughts with. I have a few novels worked up in there. I do recommend that one. As you get into your novel you can put character descriptions in there. Any thing you want to keep in mind about race or world-building.