Every now and then you stumble across a truly great idea and, as often as not, don't get it at first. Then you fall over the idea a second time and click! The light goes on. Such was my finding and re-finding of TiddlyWiki, a personal wiki system created by one Jeremy Ruston.

I'm not sure why I didn't have that "aha!" moment when I first found this free, open source software. Given the insane number of products I look at pretty much every day, however, it probably was a case of getting lost in the noise. That's a pity, because it turns out TiddlyWiki is an amazingly, perhaps insanely, great tool. In fact, I award TiddlyWiki 10 out of 5 -- it's that cool.

While I'm sure all of you know what a wiki is, here's a good definition from the Wiki mother ship, Wikipedia: "A wiki is a page or collection of Web pages designed to enable anyone who accesses it to contribute or modify content, using a simplified markup language."

TiddlyWiki takes a more personal approach to wikis than most implementations, because rather than servicing a group of users -- or, as in the case of Wikipedia, the entire galaxy -- it provides a private, single-user wiki.

TiddlyWikis can be used in a number of ways, for example, as an elegant and low-cost method for creating, distributing, and collaborating on documentation. Check out Reasoning Well, a TiddlyWiki that covers key concepts in the analysis of reasoning for philosophy students. You can use this TiddlyWiki online or download it -- and that leads to a key attribute of TiddlyWikis: Once you have your own copy, you can annotate and add to it, making it your own content mashup.

Another interesting use for TiddlyWikis is as a tool for implementing a Getting Things Done (GTD) methodology. (I recently found out that the creator of GTD, David Allen, lives just a few miles away from me. Who knew?)

If you haven't come across GTD, it's described by Wikipedia as "an action management method." If you have time- and task-management problems, you might find value in the GTD approach, as legions of techies have. For example, take a look at 43Folders, essentially a fan site for GTD and time- and process-management.

A central requirement of GTD is a system for managing tasks, keeping research and capturing notes on the stuff you need to keep track of. Not surprisingly, the simplicity, elegance and portability of TiddlyWiki make it a compelling choice for GTD adherents.