Windows only: Notes is a free, portable, no-nonsense note-taking application for Windows based on Notational Velocity (Mac only). It's fast, keyboard friendly and in the beta release supports syncing with Simplenote.
In case you missed it, Simplenote is the service I consider the Holy Grail of ubiquitous plain-text capture. With Simplenote set up and syncing between platforms, iOS devices and Android phones, you can take plain text notes in one place and access or edit those notes anywhere else you please.
Notes is simply another Windows app that plugs into Simplenote (like ResophNotes), built to mirror the functionality of the Mac-only Simplenote-syncer, Notational Velocity.
If you're a lover of plain-text note-taking, Notes is worth a look. The version that supports Simplenote is currently in beta and requires manual syncs, but eventually the Simplenote integration should be automatic. If it doesn't quite fit, I'm still working on a cross platform Adobe AIR note-taking application called Textify, so keep your eyes open for that, hopefully soon.