Trout for Mac

From Digital Dirtbag:

Trout is a mind mapping application designed to show items by category where each category has a physical attribute. You can see your nodes of information in variance of color, shape and layer. Cross links form between nodes based on text content or create your own links. This application allows the user to associate keywords in terms of shape and color and physical location. The ideas can be expanded upon and a complex model built up in a arbitrary way. URL's may be dragged or pasted into the space and they will cross link to other nodes based on the keywords and description held in the html.

The app is particularly intended for note taking during lectures or seminars. Its also useful for collecting information when researching something on the web.