I've tried a handful of notebook applications, but nothing compares to TiddlyWiki - an extremely simple yet powerful web app written mostly in JavaScript.
All you need is a single HTML file, and you're ready to start organizing your thoughts. They call it "wiki" because it's perfect for generating the collaborative Wiki format - but I use it mostly for taking notes on a variety of topics. ( I keep different files for different topics).
You don't need to know a thing about programming or how it works to use it. However, there are enough tips and techniques readily available on the web - to help you maximize your Wiki experience if you so choose.
I guarantee you'll love it - or double your money back. (Did I mention it's free?)
