Mind mapping or concept mapping tools have been around for awhile and many have suggested that they can improve learning by up to 15% (over conventional note taking). Comapping is a tool that I have recently discovered and it was love at first site. This is a really easy tool for creating outlines. Rearrange nodes (items) in your outline is a simple as drag and drop. You can expand or collapse the children of a node. Part of the tool's cool factor is the ability to attach files (images, .doc, videos) to any node. You can also format nodes with traditional formatting tools (bold, italic, color) and turn a node into a link.
For a great resource for using tools like Comapping, check out the book
Visual Tools for Transforming Information Into Knowledge by David Hyerle
Update ... I came across a post "50 Useful Mind-Mapping Tools for College Students" which shows that there are lots of choices in the Mind-Mapping/Visual Outlining space.