Boomerang for Gmail
I’ve been looking for this!
“Scheduled sending and email reminders.”
(In other words, now I can compose mails in the middle of the night — whenever the inspiration kick in — and set Boomerang to send it later, at a more decent time. Like the morning after, for instance.)
Anyway: It’s a browser extension, that interacts with Gmail and Google Apps (I use the latter in my everyday work).
Boomerang works with Chrome and Firefox. Good thing I’ve just come to really really like Chrome — both on Mac and PC, actually.