Here’s a nice, little-known gem I came across during a recent bout of outliner searching:
ThinkSheet (developed during the 90’s by Richard Marriott)
Although developed especially for special learning needs, the program turns out to be surprisingly powerful. It integrates rearrangeable notecards, mind mapping, and outlining (through sub-notecards). It can import an existing RTF document (it will just make each paragraph into a separate card), and it can export to a word processor. It’s pretty cool and appears to be well-designed. And you can use it for free for 180 days!
Incidentally, I also came across a fascinating article about outlining and the writing process by the developer of the unfortunately no-longer-available SuperText. Here’s the citation:
“A Writing Support Tool with Multiple Views”
Computers and the Humanities, Vol. 31, No. 1 (1997), pp. 13-30
I posted the full text here: http://is.gd/5cJry