There are several cool tools you can use for thinking. Two of my favorite ones are Mindmaps and Lists.
List of 100 is a great way to really stretch your mind. Here is how you do it. Take a problem or idea. Create a list of 100 things that come to your mind. In the case of a problem, it may be a hundred ways to solve it. In the case of an idea it may be a list of hundred thoughts (typically questions related to – Why, What, Who, When, How, Where).
I first came across the List of 100 here. Since then, I have created lists of 100 individually and in groups. We had great fun doing it and learned a lot. List of 100 is both a thinking tool and a group collaboration tool. Give it a try.