Of them all, I think EverNote is the most promising. I use it obsessively to keep track of almost every aspect of my life. Sample categories include projects (new home, genealogy), writing (market, research, book specific subcategories), contacts, website projects, and lots more. This program is so intuitive and simple to use, yet powerful.
Another promising program that I’ve tried out a couple of times (although I haven’t spent loads of time using it) is Text Block Writer. This one is a very close representation of a big bulletin board and a set of index cards. The freedom with which it lets you shift things around is fabulous.
Although I really liked it, I probably won’t use it much because I no longer use index cards. I used to, but once I found WriteWay Pro, I’ve had much better luck keeping all my notes together there.
I don’t imagine I’ll find something to replace WriteWay Pro any time soon. The program just works too perfectly for me and my writing style. Read my review for more details.