Evernote 
XMind
Each of these two tools is extremely powerful and combined they can change the way you organize your digital life.
Evernote and XMind. Both will help you remember all your thoughts, but each does it a little differently. Evernote is structured like a notebook so that you can add notes, images, audio and video on digital pages of your digital notebooks. Entries can be tagged and you have a choice of synchronizing in the cloud or not. If you do sync, you can do so between a mac and a pc which can be extremely helpful if you need to jump between the two. I’ve been enjoying the benefits of Evernote for about a year and have found it to be an excellent way to organize my meeting notes and to-do lists. It’s also great at capturing screenshots. I quickly downloaded the iPhone app once I heard of it and can easily say this app has changed the way I work. Using the app on my iPhone allows me to take pictures of articles or books that I later want to return to or purchase. I should also mention that text in images is also searchable within the application.
I’ve only just come across XMind as it was recently reviewed on lifehacker. This application takes the mind mapping approach to organizing all your crazy new business ideas or whatever. Based on what I’ve seen so far, I know I’ll be spending time pouring my thoughts into this cool utility.
Both are available for Mac or PC and both are FREE!