XMind is an award-winning (open source) tool you can us to jot down your ideas and brainstorm about their possibilities in a real easy way, creating great looking mind maps. One of the coolest features is the “Idea Factory”, which you can use to collect inspirations when they come to mind.
You can easily export your mind maps to Evernote and integrate them in any note or document. XMind also supports exporting to common used file formats like Microsoft Word, PowerPoint, Excel, PDF, RTF, Plain Text, HTML, PNG, JPEG, and more. Best thing to being open source is that XMind is free to download and free to use forever.