Google has released Mail Goggles, a new feature for Gmail that helps you avoid those indiscriminate moments of sending inappropriate mail.
You can go to the settings, click through to the labs, and program your Gmail account to prompt you with a skill-testing question at particular times of the week --- say, late Friday or Saturday night, when you might be a little vulnerable --- before you can press the Send button.
No, it's not a joke. Everyone I've mentioned it to so far wishes it had been here a long time ago.