Notational Velocity is a simple, perhaps even simple-minded, application for note-taking. In Mac-speak that's called "elegant." It has three panes, one to type in a search term, one to show some headings of notes, and the last for the note itself. It saves information in text format (which can be encrypted) and it has incremental search. That's it.
The program is like a card index without systematic order. Indeed, without any order at all. The chaos of notes can be navigated only by searching or browsing.
It's Amish computing or "software minimalism" at its most radical and therefore can count on a loyal congregation of the faithful and a steady trickle of curious CRIMPERS who might like the idea (but usually will soon abandon it again for what appears as greener pastures).
Nottingham, a clone of Notational Velocity, added syncing to the iPhone using Simplenote, Spotlight integration, Evernote import, and Markdown previews. It also changed the note pane to look like a yellow pad.
The most recent version of Notational Velocity follows suit and adds "native" synchronization with Simplenote, or via files with WriteRoom for iPhone and Dropbox.
Notational Velocity is freeware. Nottingham is shareware ($14.95).
There is nothing quite as elegant for the Windows platform, unless you count the freeware application Scrapbook. It has only two panes, but it sports a menu and toolbar. They are really not needed, as almost everything can be done by keyboard. The search opens a second window. Perhaps the developer, Eric Nitzsche, can be persuaded to make it look and feel even more like these two very elegant programs :).
1. See the comments for a reference to the older version of Notational Velocity.
Friday, October 29, 2010: Resophnotes is at least as elegant and available for Windows. See here. It's now at version 1.1.5.