I use this a lot for notes and programming techniques. The integration with MS Office products is handy for me, since we use MS OFfice at work. As Evan pointed out, FreeMind is a great free alternative.
I've been using this for a few years now and have found it to be really cool for storing all sorts - source code, url's images, etc. It's very flexible and highly recomended.
Cheers. Jas.