I have happily been a Gmail and Google Apps account holder for several years. A feature that I felt had been lacking was the ability to schedule emails to be sent at a later date. I've searched for various solutions ... all of them disappointing ... until recently when I came across Boomerang for Gmail which does just that; it lets you write an email now and schedule it to be sent automatically at a scheduled time. There are both Google Chrome and Firefox plugins for Boomerang. The plugin adds a “Send Later” button in Gmail. It doesn’t get much easier than that to schedule emails for sending at a later date.
If you're interested in using Boomerang for free, here's the link:
Boomerang for Gmail