It's 2 in the morning, but I've got somewhere that I like.
Vim + VimNotes + Markdown syntax colouring
Here's a screenshot of it all running via gvim. I'll probably run it under plain command-line vim, but the screenshot demonstrates the "VimNotes" menu item that lists all of the existing pages/sections.
I like the ability to search through all my pages at the touch of a button (F4) and the ability to create new ones with another (F2). Folding (like outlining, but perhaps more limited) is also good, although I'm wondering if I can tie in the Vim Outliner stuff too - at the moment, I can switch between the two by changing the filename extension, but maybe I can "embed" Outlining into any page using some custom mark-up (e.g. "[[[OTL]]]") - that would be useful, I think. Still, I prefer the readability of Markdown over the functionality of Outlining, so it's not too urgent.
I also like the direct opening of URLs in the background, and I suspect I can use Another Vim script to open just about everything else...
All I need now is to update my website to take the VimNotes headers into account, and re-convert all my existing content into compatible files, and set up CVS properly... Hurrah!