I just got blown away when I stumbled across Tiddlywiki and its many derivatives.
http://www.tiddlywiki.org
Two in particular caught my interest.
QWikiWeb
PHPTiddlywiki
QWikiWeb adds nice extra useability features, whilst PHPTiddlyWiki made me feel that this could be very straightforward to integrate into Drupal.
What Im thking is that I'd like to give members of drupal community site, the option to create as many Tiddlywiki's as they need. For themselves they could be used as planners (theres a GTDTiddlywiki too btw) or anthing else they want. But then I also wondered if the Tiddlywiki concept wouldnt be a good thing to apply to the "book" nodes, or forums or..etc etc. The neat thing that can be taken from Tiddlywiki is the ability to quickly move around a set of microcontent items within the main tiddlywiki very quickly and easily, whilst seeing each part in the context of the whole - no need to go to another page (all the contents in the same html. It may sound messy, but its not, the Tiddlywiki manages to compress a huge amount of info into a very compact view. Another aspect on the recent Tiddlywikis is that they can represent the views based on tagged content. Of course because its a wiki, all the content items can be edited double click edit , save.
There could be many ways of taking these features and applying them to drupal. If not for enhancing existing Drupal elements (such as a book or forum), then simply as an additional content item that a user can create. It would be another valuable additional personal tool over and above the users blog (or could even be used instead of). At the very least the simple scripts that make editing and other things happen so effortlessly are worth exploring. For example if we could edit drupal content so easily it would be wonderful. maybe it would mean separating out the base editing of a body of content out from all the other settings that go with a content item. One thing that came to mind was the My Workspace module which I use. If that could present and allow editing of the users content in a similar way it would be tremendous.