Comment I use Zim plus Dropbox (Score 4, Interesting) 133
I use the Zim Desktop Wiki http://zim-wiki.org/ plus Dropbox.
Zim is a graphical text editor used to maintain a collection of wiki pages. Each page can contain links to other pages, simple formatting and images. Pages are stored in a folder structure, like in an outliner, and can have attachments. Creating a new page is as easy as linking to a nonexistent page. All data is stored in plain text files with wiki formatting. Various plugins provide additional functionality, like a task list manager, an equation editor, a tray icon, and support for version control.
If you need version control, Zim supports Bazaar, Git, and Mercurial as backends.
Zim is not network aware, so I just keep its ~/Notes files in my Dropbox folder, install that and the desktop Linux/Windows/OSX Zim client as needed and I'm good to go.
Unfortunately, there is no smartphone version of Zim, but I have little need for a smartpone app of this sort. I do email myself info as needed to integrate into Zim later.