While messing around with Linux today, I ran across CherryTree (which I believe has been mentioned here before and has some pretty nifty features, particularly the ability to reorder paragraphs in a text node), and a new one called Kabikaboo (https://launchpad.net/kabikaboo a two pane note-taker with spell check and statistics. I don't think either of them is significantly better than Notecase Pro, but I'm pleased to see the continued development of this CLASS of software, available for Linux AND Windows.

Update, Kabikaboo is a very primitive novel planning program. Again, no where near as capable as many of the other tools out there. But free!