If you use mind- or context-maps to do your thinking, you would be doing yourself a favor by checking out MindMeister. I was hesitant at first because it is a web app and I generally prefer the power of a native desktop or iOS app but MindMeister’s web interface is incredibly powerful and easy to use. The sharing and team collaboration features are nothing short of amazing.
This power comes with a price, however, but I’ve said many times that if an app is truly good, you should support it so it sticks around. The Pro plan is fairly steep $9.99 a month but there is a personal account which gives you a ton of features for $5.99 a month and they have a free plan which includes some really powerful stuff (limited to three maps) for free. If you think you’re going to be doing a lot of mind mapping, this is a great way to go.