Comment on CmapTools

I've been through many apps of this type and this is my favourite (for now, at least). The things I like about it include: it's darned easy to get started; you can link all sorts of different files on your machine to your notes in the app by drag-and-drop; you can export your work to a variety of popular formats (inc PDF); the developers (a uni-based project) maintain a database of maps so that users can share their material.