AutoNotes seems to be a little-known personal wiki for OS X. It is part of the Automate suite (which I tried but found on the whole rather buggy). But AutoNotes works as a notepad for quick thoughts and notes. You just have to press F1 for creating a new note. It links automatically to existing notes.
Creation of new notes could be easier. I would prefer if it allowed enclosing words or phrases in double brackets, like nvAlt and, more importantly, ConnectedText. I like it better than nvAlt for quick notes because it is more simple (and I have no use for MultiMarkdown or extensive search abilities). It's just for quick notes and reminders that will either be deleted or imported into ConnectedText.
It saves notes as text or rtf files to any folder. I am not sure whether I need this capability. For the moment I have AutoNotes save the notes to DropBox so that they are available on any of my computers.