FreeMind - mind mapping software
I've been playing with FreeMind a free mind mapping program (and a cool name). It's written in Java, but don't let that dissuade you. The user interface is exceptionally well done. You can type in tags as quick as you can think. You can drag and drop links easily and it provides good feedback. You can work very well using only the keyboard or my using the mouse. I'm using it to keep track of notes. I'm thinking of using it to keep track of passwords as well since it has encryption. I'm using PasswordSafe at the moment which works very well and I can access with a Python program, but it's interface is less than ideal.