I'm interested in novel writing software (both for my own use, and for a class)--this is one I rather like:

http://www.spacejock.com/yWriter5.html

I am gonig to look at Hiveword a bit more--not sure about it being online.

This is another--there's a pro version which I tried out (and rather liked), but you can also use the method for free (which I've also done):

http://www.advancedfictionwriting.com/articles/snowflake-method/